US 9,031,680 B2
`(10) Patent No:
`a2) United States Patent
`Napadensky
`(45) Date of Patent:
`May12, 2015
`
`
`US009031680B2
`
`(54) SOLID FREEFORM FABRICATION USING A
`PLURALITY OF MODELING MATERIALS
`
`(71) Applicant: Objet Ltd., Rechovot (IL)
`
`Inventor: Eduardo Napadensky, Natania (IL)
`(72)
`(73) Assignee: Stratasys Ltd., Rehovet (IL)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`USC. 154(b) by 0 davs.
`.
`
`29)) Appl Nos 13/6772976
`“iled
`N
`0
`Filed:
`Nov. 15, 2012
`(22)
`(89)
`Evios Eebsication Dats
`US 2013/0073068 Al
`Mar. 21, 2013
`
`Related U.S. Application Data
`:
`Bi
`SS
`(63) Continuation of application No. 12/692,695, filed as
`application No. PCT/IL2008/001025 on Jul. 24, 2008,
`now abandoned,
`Provisional application No. 60/935,090,filed on Jul.
`25, 2007.
`
`(60)
`
`(51)
`
`(58)
`
`Int. Cl.
`(2006.01)
`G06T 17/00
`(2006.01)
`B29C 67/00
`(52) US.CL
`GO6T 17/00 (2013.01); B29C 67/0059
`CPC
`— (2013.01); B90 67/0092 (2013.01)
`Field ofClassificationSearch
`~
`CPC veecceee B29C 67/0055; B29C 67/0059; B29C
`67/0092; GO6T17/00; GO6T 19/00; GO6T
`2219/2016; GO5B 19/4097; GO5B 19/4099;
`GOSB 2219/35066; GO5B 2219/49013; GO3F
`7/0037
`
`
`
`USPC ue. 700/95-98, 106, 117-124, 159, 163:
`706/903, 904, 919; 703/1; 264/401
`See applicationfile for complete searchhistory,
`
`........... 700/119
`
`References Cited
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`(Continued)
`FOREIGN PATENT DOCUMENTS
`2004-090530
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`WO 2004/096527
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`WO 2009/013751
`1/2009
`OTHER PUBLICATIONS
`
`(56)
`
`JP
`WO
`WO
`
`Communication Pursuant to Article 94(3) EPC Dated Jul. 6, 2011
`From the European Patent Office Re. Application No. 08776652.3.
`(Continued)
`
`Primary Examiner —MLN. Von Buhr
`ae
`x
`6)
`pee
`A system and methods for solid freeform fabrication of an
`object is disclosed. The system comprises a solid freeform
`fabrication apparatus having a plurality of dispensing heads,
`4 building material supply apparatus configured to supply a
`plurality of building materials to the fabrication apparatus,
`and a control unit configured for controlling the fabrication
`apparatus and the supply apparatus based on an operation
`mode selected from a plurality of predetermined operation
`modes,
`
`27 Claims, 14 Drawing Sheets
`
`radiations
`OUTCe
`“28
`
`Shenzhen Tuozhu 1005
`
`1
`
`Shenzhen Tuozhu 1005
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`

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`US 9,031,680 B2
`Page 2
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`(56)
`
`References Cited
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`U.S. PATENT DOCUMENTS
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`ee 7103/6
`6,813,594 B2*
`........
`11/2004 Guertin etal.
`433/24
`6,846,179 B2*
`1/2005 Chapouland etal.
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`00/119
`6,882,895 Bl*®
`4/2005 Knoppers et al. wu...
`6,898,477 B2
`§/2005 Loughran
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`7,280,990 B2
`10/2007 Turneretal.
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`11/2007 Napadenskyetal.
`7,369,915 B2*
`........ 700/118
`5/2008 Kritchman et al.
`7,371,073 B2*
`.. 439/66
`5/2008 Williams ......
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`we 1703/1
`..
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`7,542,817 B2*
`.. 700/98
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`7,758,351 B2*
`7/2010 Brownet al. ccccisenes 439/66
`7,890,303 B2
`2/2011 Matsuda
`$584,353 B2* 11/2013) Williams ......000.cuu. 29/852
`2004/0187714 Al
`9/2004 Napadenslyetal.
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`1/2005 Krameretal. ........ a 264/401
`2005/0012247 Al*
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`1/2005 Gurovich .....cse woe 264/488
`2005/0017414 AL*
`2005/007 1135 Al
`3/2005 Vredenburgh et al.
`OTHER PUBLICATIONS
`
`International Preliminary Report on Patentability Dated Mar. 11,
`2010 From the International Searching Authority Re: Application
`No. PCT/IL2008/00 1025,
`International Search Report and the Written Opinion Dated Feb. 26.
`2010 From the International Searching Authority Re.: Application
`No. PCT/IL2008/001025,
`Official Action Dated May 17, 2012 From the US Patent and Trade-
`mark Office Re, U.S. Appl. No. 12/692,695.
`Response Dated Jan, 5, 2012 to Communication Pursuant to Article
`94(3) EPC of Jul. 6, 2011 From the European Patent Office Re.
`Application No, 08776652,3.
`Communication Pursuant to Article 94(3) EPC Dated Oct. 22, 2013
`From the European Patent Office Re. Application No. 08776652.3.
`European Search Report and the European Search Opinion Dated
`Oct. 22, 2013 From the European Patent Office Re. Application No.
`13176069.6.
`European Search Report and the European Search Opinion Dated
`Oct. 22, 2013 From the European Patent Office Re. Application No.
`13176072.0.
`Communication Pursuant to Rules 70(2) and 70a(2) EPC and Refer-
`ence to Rule 39(1) EPC Dated Nov. 25, 2013 From the European
`Patent Office Re. Application No. 13176069.6.
`Communication Pursuant to Rules 70(2) and 70a(2) EPCand Refer-
`ence to Rule 39(1) EPC Dated Nov. 25, 2013 From the European
`Patent Office Re. Application No. 13176072.0.
`
`Communication Relating to the Results of the Partial International
`Search Dated Nov. 9, 2009 From the International Searching Author-
`ity Re.: Application No. PCT/IL2008/00 1025,
`
`* cited by examiner
`
`2
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`define a plurality of sub-regions within each region and attribute a property to each
`sub-region
`
`input data pertaining to shapes of an object and eachofa plurality of regionsof the
`object
`
`according the input data and the sub-region to form the three-dimensional object
`
`select a modeling material and/or a modeling material combination according to the
`attributed property of each sub-region
`
`dispense the selected modeling materials or combinations in a layerwise manner
`
`Fig. 22
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`US 9,031,680 B2
`
`1
`SOLID FREEFORM FABRICATION USING A
`PLURALITY OF MODELING MATERIALS
`
`RELATED APPLICATIONS
`
`This application is a continuation ofU.S, patent applica-
`tion Ser. No. 12/692.695to filed on Jan. 25, 2010, which is a
`continuation of PCT Patent Application No. PCT/IL2008/
`001025 having International Filing Date of Jul. 24, 2008,
`whichclaims the benefit ofpriority ofU.S. Provisional Patent
`Application No. 60/935,090 filed on Jul, 25, 2007. The con-
`tents of the above applicationsare all incorporated herein by
`reference.
`
`FIELD AND BACKGROUND OF THE
`INVENTION
`
`‘The present inventionrelates to solid freeform fabrication
`and, moreparticularly, to a solid freeform fabrication using a
`plurality of modeling materials.
`Solid Freeform Fabrication (SFF) is a technology enabling
`fabrication ofarbitrarily shapedstructures directly from com-
`puterdata via additive formation steps. The basic operation of
`any SFF system consists of slicing a three-dimensional com-
`puter modelinto thin cross sections, translating the result into
`two-dimensionalposition data and feeding the data to control
`equipment whichfabricatesa three-dimensional structure ina
`layerwise manner,
`different
`entails many
`Solid
`freeform fabrication
`approaches to the method offabrication, including three-
`dimensionalprinting, electron beam melting, stereolithogra-
`phy,selective laser sintering, laminated object manufactur-
`ing, fused deposition modeling and others.
`In three-dimensional printing processes, for example, a
`building material is dispensed from a dispensing head having
`a set ofnozzles to deposit layers on a supportingstructure.
`Depending on the building material, the layers may then be
`cured or solidified using a suitable device. The building mate-
`rial may include modeling material. which forms the object,
`and support material, which supports the object as it is being
`built. Various three-dimensionalprinting techniquesexist and
`are disclosed in, e.g., U.S. Pat. Nos. 6,259,962, 6,569,373,
`6,658,314, 6,850,334, 6,863,859, 7,183,335 7,209,797,
`7,300,619 and 7,225,045 and U.S. Published Applications
`Nos. 20050104241 and 20060054039, all of the same
`Assignee, the contents of which are hereby incorporated by
`reference.
`Solid freeform fabrication is typically used in design-re-
`lated fields whereit is used for visualization, demonstration
`and mechanical prototyping. Thus, SFFfacilitates rapid fab-
`ricationof functioning prototypes with minimal investmentin
`tooling and labor. Such rapid prototyping shortens the prod-
`uct development cycle and improves the design process by
`providing rapid and effective feedback to the designer. SFF
`can also be used for rapid fabrication of non-functional parts,
`e.g., for the purpose ofassessing various aspects of a design
`such as aesthetics, fit, assembly and the like. Additionally,
`SFF techniques have beenproven to be useful in the fields of
`medicine, where expected outcomes are modeled prior to
`performingprocedures.It is recognized that many other areas
`can benefit from rapid prototyping technology, including,
`without limitation, the fields of architecture, dentistry and
`plastic surgery where the visualization ofa particular design
`and/or function is useful.
`different
`and
`improvements
`Although
`numerous
`approaches which have been developed over the years for
`
`if
`
`to
`
`[eyi}
`
`2
`solid freeform fabrication, the number of techniques which
`allow the additive formation ofobjects using more than one
`modeling material is limited.
`U.S. Pat. No. 5,149,548 of Yamaneetal., for example,
`discloses a three-dimensional printing technique using two-
`part curable material. The material is jetted from anink jet
`head to a stage and laminated thereon. The ink jet head is
`disposed underthe stage, suchthat the two-part curable mate-
`rial is jetted from a downwardsideto an upwardside andis
`cured every jetting process. The apparatus may include sev-
`eral inkjet nozzles and the two-part curable material can be
`exchanged for anotherduringthe process, Since thejetting is
`from a downward sideto an upward side, a newly-exchanged
`two-part curable material is not mixed or combined with the
`previously-used two-part curable material.
`U.S. Pat. No, 6,508,971 of Leydenetal., discloses a tech-
`niguelor creating a three-dimensional object by depositing a
`build material on a working surface from a plurality ofdis-
`pensing orifices in a print head. The build material is selec-
`tively dispensed from the print head while scanning the work-
`ing surface. Subsequently, the print head is repositioned and
`the scan is repeated along a path whichis offset from the
`previous path. The scans are repeated until the three-dimen-
`sional object is formed. ‘The disclosure contemplates the use
`to wn
`5 of different materials ondifferent raster lines or drop loca-
`tions.
`U.S. Pat. No, 6,658,314 of Gothait et al, and incorporated
`herein by reference,
`to discloses a printing system and a
`method for printing complex three-dimensional models uti-
`lizing two dispensing heads whicheject building material. A
`“modeling” materialis dispensed from a dispensing head, and
`a “support” material is dispensed from a second dispensing
`head. The two materials may be combined to produce layers
`for forming the three-dimensional model, while a different
`combination is used to build the support structure or the
`release structure.
`The two building materials may have different hardness
`characteristics so as to control the hardnessof the layers. The
`construction layers of the model are formed with a harder
`modulus of elasticity than the release layers.
`U.S. Pat. No. 7,300,619, of the present Assignee, the con-
`tents ofwhichare hereby incorporated byreference,discloses
`apparatus for management and control of the supply of build-
`ing materials to three-dimensionalprinting systems. A supply
`system having a set ofvalves or a valve matrix is used for
`controlling the supply. Managementand contro! of materials
`are achieved by measuring data on the status ofbuilding
`material in the printing cartridge or the supply system, and
`processing the building material status data to determine
`parameters of the building material. The supply system can
`include several cartridges each containing one typeofbuild-
`ing material, either modeling material or support material.
`Different cartridges can contain different types of materials
`and colors.
`
`at
`
`5
`
`eai
`
`eo) 5
`
`60
`
`U.S. Published Application No. 20040187714 ofthe same
`Assigneespecifies use ofmodeling materials having different
`properties, in different combinations, in order to obtain dif-
`ferent regions, forming a homogeneous or non-homogeneous
`three-dimensional structure in which different regions may
`be structurallydifferent, chemically different or have differ-
`ent properties. The different combinations comprise compos-
`ite materials having properties that vary within the material.
`U.S. Published Application No. 20060159869 of Kramer
`et al., discloses a solid freeform fabrication technique in
`which two reactive build compositions which include the
`same material property but with differentattributes (typically,
`one composition is mechanically flexible while the other is
`
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`US 9,031,680 B2
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`3
`mechanically rigid), are dispensed onto a substrate to form a
`mixed composition. The mixed composition is subsequently
`cured to form a layer of cured composition, which includes
`the same material property but with anattribute whichdiffers
`from, and depends upon the respective amounts ofeach of the
`individual attributes ofthe dispensed compositions, The dis-
`closure also contemplates the solid freeform fabrication of
`three-dimensional objects having regions which varyin the
`material property.
`U.S, Pat, No. 7,500,846 ofthe present Assignee, the con-
`tents of which are hereby incorporated by reference, teaches
`the use of one or more types of photopolymers dispensed
`separately or together, simultaneously or consecutively.
`U.S. Pat. No. 6,989,115 (Russell et al.) discloses a three-
`dimensional printer including multiple printheads for print-
`ing binder and/or colorant onto a bed ofbuild material in a
`build chamber. The printer can include determining the total
`amount of binderliquid needed to solidify the build material
`Ea
`at the particular location, determining the amount of each of >
`the colored binderliquids needed to produce the desired color
`at the particular location and determining the amountof col-
`orless binder liquid that needs to be added to the colored
`binderliquids to obtain the predetermined total binderliquid
`requirement.
`
`SUMMARYOF THE INVENTION
`
`o
`
`It was found by the inventors of the present invention that
`the throughput associated with traditional
`techniques in
`which more than one modeling material is used for the fab-
`rication ofan objectis considerably lower comparedto single
`modeling material techniques. The present inventors also
`found that the numberof building materials that can be used
`or produced in conventional techniques is very limited, and
`the properties ofthe materials that can be obtainedare still far
`inferior compared to the properties of standard engineering
`polymers.
`‘The present invention provides system and methods suit-
`able for solid freeform fabrication. The system comprises
`solid freeform fabrication apparatus having a plurality of
`dispensing heads. The system preferably has two or more
`modes of operation, in whichina first operation modeall the
`dispensing heads of the system are operational throughout a
`building scan cycle in each location of the layer, and in a
`second operation mode at least one dispensing head ofthe
`system is not operative during at least a part ofthe building
`scan cycle ofthe layer.
`In various exemplary embodiments of the invention, the
`un
`first operation modeis used for fabricating objects made of'a 5
`single material, e.g., a single modeling material, to and the
`second operation modeis used for fabricating objects made of
`two or more materials, e.g. two or more modeling materials.
`In some embodiments ofthe invention,the first operation
`mode is used for fabricating objects using a combination of
`equal amounts of more than one modeling material, wherein
`the combination is produced by dispensing the different
`materials fromdifferent dispensing heads, to form a single
`uniform material after deposition.
`In some embodiments, the second operation modeis used
`for fabricating objects using two or more modeling materials
`in different predetermined combinations, wherein the com-
`binations are produced by dispensing the different modeling
`materials from different dispensing heads.
`In some embodiments, the second operation modeis used
`for the simultaneous building of more than one object, each
`object being fabricated using a different modeling material or
`
`at
`
`aH45
`
`55
`
`60
`
`4
`a different modeling material combination, wherein the com-
`bination is produced by dispensing different materials from
`different dispensing heads.
`In some embodiments, the second operation modeis used
`for the simultaneousbuilding ofdifferent areas or regions of
`a single object, each area or region being fabricated using a
`different modeling material or a different modeling material
`combination.
`The mode ofoperationcan be selected automatically by the
`system or may be selected by the operator, according to the
`final modelor object desired to be produced. For example, the
`system can automatically choose the first operation mode
`when the object/s or parts thereof to be fabricated are speci-
`fied as built of the samesingle modeling material, and when
`this modeling material is already fed into all the modeling
`material dispensing heads, or when it is desired to build an
`object using an uniform mix of the modeling materials
`already fed into the modeling material dispensing heads.
`In the first operation mode, an object formed of a single
`modeling material may be fabricated for exampleby dispens-
`ing a single modeling material via all ofthe dispensing heads.
`Alternatively,in the first operation mode, an object made of a
`mix of modeling materials can be fabricated in first operation
`mode using two or more modeling materials, where, for
`example,
`two different modeling materials are dispensed
`from different dispensing heads, simultaneously and in equal
`amounts throughout the to object, to form a uniform mix of
`materials.
`In some embodiments ofthe invention an objectis fabri-
`cated by dispensing two or more materials, each from a dif-
`ferent dispensing head, where one or both ofthe materials
`may have a valuable property, but not have the properties
`required to function as a modeling materialon its/their own.
`In these embodiments the combination of the two materials
`provides the properties required to build the desired object.
`One example is dispensing liquid resin froma first head and
`dispensing liquid hardener from a second head, where the
`combination ofboth leads to a solid material.
`In another embodiment, one of the materials may be non-
`solidifiable, while the other material is solidifiable. ‘Thefirst
`
`material is non-solidifiable in that it does not solidify during
`the fabrication process, bul remains in liquid, gel, paste or
`other non-solid or semi-solid form. The second material is
`solidifiable in that it can be solidified by an appropriate solidi-
`fication procedure. The solidifiable material can fully sur-
`round or contain the non-solidifiable material, The non-so-
`lidifiable material
`can remain within the object, or
`alternatively be drained, burnt out or otherwise removed once
`the process is complete. In this way, for example, a hollowor
`porous model can be provided.
`In some embodiments, two materials are non-solidifiable
`but their combinationis solidifiable.
`In some embodiments, at least one of the modeling mate-
`rials has a required property other than a building property.
`For example, the surrounded (“contained”) material may be a
`material which has a valuable property,e.g., biological, phar-
`maceutical, or other activity, and the “containing” structure
`and material type allow the release ofthe contained material
`overtime, e.g. controlled release or sustained release or slow
`release of the material, in order to enable it, for example, to
`expressits biological or pharmaceutical activity, according to
`its intended use. All these alternatives can be carried out inthe
`second operation mode ofthe present embodiments.
`The second operation mode provides various options to
`operate the system.In one embodiment, the system fabricates
`objects which have different parts consisting of different
`materials, ¢.g., two separate parts ofa specific object, each
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`5
`part consisting of a different modeling material. In another
`embodiment, an object may have two parts, each of which
`may consist of a different combination of more than one
`modeling material. In an additional embodiment, a number of
`different objects are to simultaneously fabricated ona single
`working surface or tray, where some objects on the tray are
`made ofa single modeling material while others are made of
`another single material or different combinations of more
`than one modeling material.
`Preferred embodiments of the invention provide the possi-
`bility to fabricate an object made of a composite material,
`which is comprised oftwo or moreindividual modeling mate-
`rials having different properties. The individual modeling
`materials are selected for use on thebasis oftheir properties
`so as to obtain a material with a third, different property or a
`combinationoftheir properties. The composite material can,
`for example, havea property or properties different to those of
`each ofthe two or more individual modeling materials used,
`depending onthe relative amounts of each individual model-
`ing material dispensed and the order or “structure” oftheir
`deposition,
`The ability of the system of the present embodimentsto
`utilize two or more different modeling materials, makes it is
`possible to use and/or produce many more, and more varied
`materials in solid freeform fabricationthan has been possible
`to date in conventional solid freeform fabrication techniques,
`as well as providing many different possibilities for combin-
`ing multiple materials, according to the final object and/or
`object properties desired to be obtained.
`The ability of the system of the present embodimentsto
`utilize two or moredifferent modeling materials, allows the
`fabrication of parts or objects having properties which are
`difficult, if not impossible,
`to achieve using conventional
`solid freeform fabrication techniques. For example, modeling
`materials which have a great tendency to shrink as a result of
`the polymerization process are not usually suitable for use in
`traditional solid freeform fabrication apparatus. A modeling
`material suffering from high shrinkage during solidification
`makes especially difficult the manufacturing of bulky three
`dimensional geometries but may allow the fabrication ofthin
`shell like three dimensional geometries, for example, around
`a bulky object whichis fabricated of a material with accept-
`able shrinkage. The system of the present embodiments use-
`fully provides a solution to this problem. For example, the
`system of the present embodiments can fabricate parts or
`objects in whichthe surfaces ofthe part or object are made of
`one material, while the internal regions ofthe part or object
`comprise a different material. In this example, the internal
`regions may befabricated of a material which lacks mechani-
`un
`cal strength, such as a gel or liquid. but having other desirable 5
`properties such as being easily burt without leaving ash or
`othertraces.
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`The ability of the system of the present embodiments to
`utilize two or more different modeling materials, also allows
`the fabrication ofobjects via a segmentation process, wherein 5
`layers are built
`in segments or “tiles”. Such process is
`described in U.S. Application No. 60/430,362 and U.S. Pat.
`No. 7,300,619, the contents of whichare hereby incorporated
`by reference. The segmentsortiles may be comprised ofone
`material, andjoined by dispensing a different material, e.g., a
`binder or glue-like material, in the breaks betweenthe seg-
`ments. By building in smaller segmentsortiles instead of a
`full layer, this method serves to overcome problemsof mate-
`rial shrinkage which may occur during the curing process.
`According to the present embodiments, the digital repre-
`sentation of a three-dimensional object may be created by
`using suitable software such as CAD (Computer Aided
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`Design) software, a scanning system, or an imaging system
`e.g., CT system or MRI system, which produces data which
`may be converted to a standard communicationfile format,
`e.g., STL (Standard Tessellation Language) format, legible
`by the solid freeformfabrication apparatus. STL files are read
`by the system of the present embodiments and ‘sliced’ into
`thin layers (also referred to as slices). A controller preferably
`converts the thin slices into physical layers ofbuilding mate-
`rial to be deposited, accordingtothe digital slices, during the
`course offabricating the three-dimensionalobject.
`The STL file may include information regarding a number
`of separate regions, Typically, an object is communicated
`from CAD to an SFF machine by a single STL file. After
`retrieving region information from that STL (or specifying
`regions by other means) the object information can be saved
`asa bunchofSTLfiles, each ofwhich describes a regionin the
`object, and all having commoncoordinate system andorigin.
`The process ofretrieving regions in an object from an STL file
`maybe carried out generally as knownin the art, for example,
`as described in U.S. Pat. No. 5.768.134, assigned to Materia-
`lise N.V.
`Before fabrication, the virtual object is preferably ‘sliced’
`by the system into thin slices, which may be described as
`bitmaps, and transferred to the fabrication engine for trans-
`forminginto layers forming the three-dimensional object.
`In a preferred embodiment of the present invention, the
`specific modeling to materials to be used, and their combina-
`tion and/or spatial deposition within the object layer are
`defined in the system’s softwarefor eachregion,according to
`the pre-defined properties desired for each part of the final
`object. For example, in a preferred embodiment, an STL is
`divided by an SFF systeminto a number of new STL-s, each
`defining a sub region in the object. The new STLsare then
`assembled to form a group of STLs. whichdescribe the same
`original object. Then, a modeling material or modeling mate-
`rial combinationto be used inthe fabrication ofeach new STL
`is assigned to each STL. The systemthenslices the group of
`STLs. The resulting slices are in-turn divided into respective
`slices for each of the different dispensing heads. Finally the
`system sendsthe slices to the fabrication apparatus orprinter
`to build layers of material. In another embodiment, a set of
`communication files, for example, a set of STLfiles, each
`defining a region in the object and referring to a common
`coordinate system and origin, is prepared by the object design
`software, ie, CAD software.
`In analternative embodiment, for any givenregion, a user
`or operator ofthe apparatus ofthe invention may introduce
`user-defined definitions, e.g., via user interface software for
`the apparatusofthe invention. For example, a user or operator
`may select a specific region and define within the region,
`sub-areas ofthe region, and select modeling materials and/or
`modeling material combinations for the thus defined sub-
`areas of the region, according to the properties desired for
`each respective sub-area. One exampleof this is defining one
`modeling material or material combinationfor the boundary
`of the region and a different modeling material or material
`combinationfor the inside ofthe region.
`According to an aspect of some embodiments of the
`present inventionthere is provided a systemforsolid freeform
`fabrication ofan object. The system comprises: a solid free-
`formfabrication apparatus having a plurality of dispensing
`heads; a building material supply apparatus configured to
`supply a plurality of building materials to the fabrication
`apparatus; and a control unit configured for controlling the
`fabrication apparatus and the building material supply appa-
`ratus, based on an operation modeselected from a plurality of
`predetermined operation modes.
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`According to some embodiments ofthe invention the plu-
`rality of operation modes comprisesat least a first operation
`modein whichall dispensing heads operate to during a single
`building sean cycle ofthe fabrication apparatus, and a second
`operation mode in whichat least one dispensing head is not
`operative during at least a part of the single building scan
`cycle.
`According to an aspect of some embodiments of the
`present invention there is provided a method of fabricating a
`three-dimensional object. comprising operating the system so
`as to form the three-dimensional object.
`According to some embodiments ofthe present invention
`at least one operation mode allows the dispensing heads to
`dispense one type of modeling material and a support mate-
`rial.
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`capable of accessing a pixel map characterized by an even
`density of pixels, and composed of N different head pixel
`maps, each corresponding to a different dispensing head.
`According to some embodimentsof the inventionat least
`one operation mode is characterized in that all head pixel
`mapsare similar to each other and include substantially the
`same numberof pixels.
`According to some embodiments of the invention at least
`one operation modeis characterized in that at least two head
`pixel mapsdiffer from each other and include different num-
`ber ofpixels.
`According to some embodiments ofthe present invention
`the supply apparatus comprises a building material flow unit,
`controllable by the control unit and arranged for selectively
`allowing flow ofbuilding materials to the fabrication appara-
`tus.
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`According to some embodimentsof the inventionthe sup-
`ply apparatus comprisesa plurality of containers for holding
`the plurality of building materials, and whereinthe flowunit
`is arranged to allowflow of different building materials to
`different dispensing heads.
`According to some embodiments ofthe invention the sup-
`ply apparatus comprise a plurality of containers for holding
`the plurality of building materials, and wherein the flowunit
`is characterized byatleasta first state and a secondstate, the
`second state being defined such that at least two different
`dispensing headsare fed by different modeling materials, and
`thefirst state being defined suchthat all dispensing heads are
`supplied by the same modeling material.
`According to some embodiments ofthe present invention
`the control unit is configuredto allow dispensing ofmore than
`one modeling material at the same time.
`According to some embodiments ofthe present invention
`the control unitis operative to dynamically change the opera-
`tion mode by selecting a different operation mode from the
`plurality of operation modes.
`According to some embodiments of the invention the
`selection of the different operation modeis according to the
`numberofdifferent modeling materials being dispensed by
`the dispensing heads.
`According to some embodimentsofthe presentinvention
`the plurality of dispensing heads comprises a plurality of
`modeling heads having a total of N nozzle arrays, wherein the
`nozzles in each array are disposed along an indexing diree-
`tion, the plurality of modeling heads being operable to scan a
`working surface along a scanning direction being at an angle
`to the indexing direction so as to form on the