Source: http://patents.com/us-9919474.html
Timestamp: 2018-12-12 01:09:43
Document Index: 273625355

Matched Legal Cases: ['Application No. 13176072', 'Application No. 08776652', 'Application No. 08776652', 'Application No. 13176069', 'Application No. 13176072', 'Application No. 08776652', 'Application No. 60', 'Application No. 60']

US Patent # 9,919,474. Solid freeform fabrication using a plurality of modeling materials - Patents.com
United States Patent 9,919,474
Napadensky March 20, 2018
Family ID: 1000003185881
14/680,100
US 20150210010 A1 Jul 30, 2015
13677376 Nov 15, 2012 9031680
12692695 Jan 25, 2010
PCT/IL2008/001025 Jul 24, 2008
60935090 Jul 25, 2007
Current CPC Class: B29C 64/112 (20170801); B29C 64/40 (20170801); B29C 67/202 (20130101); G06T 17/00 (20130101); B29C 64/268 (20170801); B29C 64/393 (20170801); B29C 64/20 (20170801); B29K 2105/0058 (20130101); B29K 2105/24 (20130101); B33Y 30/00 (20141201); B33Y 50/02 (20141201); Y10T 428/24802 (20150115); B33Y 10/00 (20141201)
Current International Class: B29C 67/00 (20170101); B29C 67/20 (20060101); B29C 64/112 (20170101); G06T 17/00 (20060101); B29C 64/40 (20170101); B33Y 30/00 (20150101); B33Y 50/02 (20150101); B33Y 10/00 (20150101)
Field of Search: ;264/49,308
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WO 2009/013751 Jan 2009 WO
Communication Pursuant to Article 94(3) EPC dated Apr. 19, 2017 From the European Patent Office Re. Application No. 13176072.0. (5 Pages). cited by applicant .
Communication Pursuant to Article 94(3) EPC dated Jul. 6, 2011 From the European Patent Office Re. Application No. 08776652.3. cited by applicant .
Communication Pursuant to Article 94(3) EPC dated Oct. 22, 2013 From the European Patent Office Re. Application No. 08776652.3. cited by applicant .
Communication Relating to the Results of the Partial International Search dated Nov. 9, 2009 From the International Searching Authority Re.: Application No. PCT/IL2008/001025. cited by applicant .
European Search Report and the European Search Opinion dated Oct. 22, 2013 From the European Patent Office Re. Application No. 13176069.6. cited by applicant .
European Search Report and the European Search Opinion dated Oct. 22, 2013 From the European Patent Office Re. Application No. 13176072.0. cited by applicant .
International Preliminary Report on Patentability dated Mar. 11, 2010 From the International Searching Authority Re.: Application No. PCT/IL2008/001025. cited by applicant .
International Search Report and the Written Opinion dated Feb. 26, 2010 From the International Searching Authority Re.: Application No. PCT/IL2008/001025. cited by applicant .
Official Action dated Jun. 12, 2014 From the U.S. Patent and Trademark Office Re. U.S. Appl. No. 13/677,376. cited by applicant .
Official Action dated May 17, 2012 From the U.S. Patent and Trademark Office Re. U.S. Appl. No. 12/692,695. cited by applicant .
Official Action dated Nov. 25, 2013 From the U.S. Patent and Trademark Office Re. U.S. Appl. No. 13/677,376. cited by applicant .
Communication Pursuant to Article 94(3) EPC dated Jan. 16, 2017 From the European Patent Office Re. Application No. 08776652.3. (4 Pages). cited by applicant.
This application is a continuation of U.S. patent application Ser. No. 13/677,376 filed Nov. 15, 2012, now U.S. Pat. No. 9,031,680, which is a continuation of U.S. patent application Ser. No. 12/692,695 filed on Jan. 25, 2010, now abandoned, which is a continuation of PCT Patent Application No. PCT/IL2008/001025 having International Filing Date of Jul. 24, 2008, which claims the benefit of priority of U.S. Provisional Patent Application No. 60/935,090 filed on Jul. 25, 2007.
1. A method of solid freeform fabrication, comprising: dispensing a modeling material, a support material, and at least one additional material that cannot function as a modeling material and cannot function as a support material on its own, at least partially solidifying said modeling material, such as to form a three-dimensional object, and removing said at least one additional material to form a porous or hollow three-dimensional object.
2. The method of claim 1, wherein said at least one additional material is at least partially interlaced with said modeling material, and wherein said removing forms a porous three-dimensional object.
12. The method of claim 1, wherein said removing is by draining.
13. The method of claim 1, wherein said removing is by burning.
14. A method of solid freeform fabrication, comprising: dispensing at least two non-solidifiable materials that that combine after said dispensing to form a solidifiable mixture, and at least partially solidifying said solidifiable mixture, such as to form a three-dimensional object.
U.S. Pat. No. 6,658,314 of Gothait et al. and incorporated herein by reference, discloses a printing system and a method for printing complex three-dimensional models utilizing two dispensing heads which eject building material. A "modeling" material is 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.
In another embodiment, one of the materials may be non-solidifiable, while the other material is solidifiable. The first material is non-solidifiable in that it does not solidify during the fabrication process, but 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 solidification procedure. The solidifiable material can fully surround or contain the non-solidifiable material. The non-solidifiable 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 hollow or porous model can be provided.
In some embodiments, at least one of the modeling materials 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, pharmaceutical, or other activity, and the "containing" structure and material type allow the release of the contained material over time, e.g. controlled release or sustained release or slow release of the material, in order to enable it, for example, to express its biological or pharmaceutical activity, according to its intended use. All these alternatives can be carried out in the second operation mode of the present embodiments.
Preferred embodiments of the invention provide the possibility to fabricate an object made of a composite material, which is comprised of two or more individual modeling materials having different properties. The individual modeling materials are selected for use on the basis of their properties so as to obtain a material with a third, different property or a combination of their properties. The composite material can, for example, have a property or properties different to those of each of the two or more individual modeling materials used, depending on the relative amounts of each individual modeling material dispensed and the order or "structure" of their deposition.
The ability of the system of the present embodiments to utilize two or more different modeling materials, also allows the fabrication of objects via a segmentation process, wherein 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 which are hereby incorporated by reference. The segments or tiles may be comprised of one material, and joined by dispensing a different material, e.g., a binder or glue-like material, in the breaks between the segments. By building in smaller segments or tiles instead of a full layer, this method serves to overcome problems of material shrinkage which may occur during the curing process.
According to the present embodiments, the digital representation of a three-dimensional object may be created by using suitable software such as CAD (Computer Aided 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 communication file format, e.g., STL (Standard Tessellation Language) format, legible by the solid freeform fabrication 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 of building material to be deposited, according to the digital slices, during the course of fabricating the three-dimensional object.
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 transforming into layers forming the three-dimensional object.
According to some embodiments of the invention the N is a power of 2, and wherein the N nozzle arrays of modeling material are sequentially ordered with respect to the scanning direction at locations 1 to N such that rows formed by any nozzle array of modeling material at location K are symmetrically disposed between rows formed by all nozzle arrays of modeling material at locations 1 to K-1.
According to some embodiments of the invention regions having different modeling material combinations that touch each other are rescaled according to a common resealing factor.
FIG. 5 is a schematic illustration of the supply apparatus and the dispensing heads in a preferred embodiment in which there are four modeling heads, each composed of two nozzle arrays, and one support head composed of eight nozzle arrays;
FIGS. 6-7 are schematic illustrations of the registration of the nozzle arrays of the various dispensing heads along the indexing direction Y, according to various exemplary embodiments of the present invention;
FIG. 8 is a schematic illustration of a cross section of an object having a buffer layer near the outer surfaces of the object, according to various exemplary embodiments of the present invention;
FIG. 9 is a schematic illustration of a three-dimensional object fabricated by SFF, having a pattern formed on its surface;
FIGS. 10a-b are schematic illustrations of cross sections of a deep pattern;
FIG. 11 is a schematic illustration of an object shaped as a cube made of composite material;
FIGS. 12a-b are schematic representations of bitmaps for two materials in a dispersed phase material structure, according to various exemplary embodiments of the present invention;
FIGS. 13a-b are schematic representations of bitmaps for two materials in laminate (XY) model structure, according to various exemplary embodiments of the present invention;
FIGS. 14a-b are schematic representations of bitmaps for two materials in IPN model structure, according to various exemplary embodiments of the present invention;
FIG. 15 is a schematic illustration of a construction according to the bitmap shown in FIG. 14a;
FIG. 16 is a schematic illustration of a construction according to the bitmap shown in FIG. 14b;
FIG. 17 is a schematic illustration of a construction according to the bitmap shown in FIGS. 14a-b;
FIG. 18 is a schematic illustration of construction of a first material in an IPN model structure;
FIG. 19 is a schematic illustration of construction of a second material in an IPN model structure;
FIG. 20 is a schematic illustration of construction of a first material and a second material in an IPN model structure;
FIGS. 21a-b are schematic illustrations of a side view (FIG. 21a) and a top view (FIG. 21b) of a printing device, according to various exemplary embodiments of the present invention; and
FIG. 22 is a flowchart describing a method of solid freeform fabrication of an object, according to embodiments of the present invention.
System 10 comprises a solid freeform fabrication apparatus 14 having a plurality of dispensing heads 21. Each head preferably comprises one or more nozzle arrays 22, through which a building material 24 is dispensed. Head 21 is better illustrated in FIGS. 1b-c, showing a dispensing head with one (FIG. 1b) or two (FIG. 1c) nozzle arrays.
Preferably, but not obligatorily, apparatus 14 is a three-dimensional printing apparatus, in which case dispensing heads 21 are printing heads, and the building material is dispensed via inkjet technology. This need not necessarily be the case, since, for some applications, it may not be necessary for the solid freeform fabrication apparatus to employ three-dimensional printing techniques. Representative examples of solid freeform fabrication apparatus contemplated according to various exemplary embodiments of the present invention include, without limitation, binder jet--powder base apparatus and fused deposition modeling apparatus.
Each dispensing head is optionally and preferably fed via a building material reservoir (not shown, see FIGS. 3a-c and 4a-c) which may optionally include a temperature control unit (e.g., a temperature sensor and/or a heating device), and a material level sensor. To dispense the building material, a voltage is applied to the dispensing heads to selectively deposit droplets of material via the dispensing head nozzles, for example, as in piezoelectric inkjet printing technology. The dispensing rate of each head depends on the number of nozzles, the type of nozzles and the applied voltage. Such dispensing heads are known to those skilled in the art of solid freeform fabrication.
Preferably, but not obligatorily, the overall number of dispensing nozzles or nozzle arrays is selected such that half of the dispensing nozzles are designated to dispense support material and half of the dispensing nozzles are designated to dispense modeling material. In the representative example of FIG. 1d, three dispensing heads 21a, 21b and 21c are illustrated. Each of heads 21a and 21b has one nozzle array, while head 21c has two nozzle arrays. In this Example, heads 21a and 21b can be designated for modeling material and head 21c can be designated for support material. Thus, head 21a can dispense a first modeling material, head 21b can dispense a second modeling material and head 21c can dispense support material. In an alternative embodiment, head 21c, for example, may comprise 2 physically separate structures, each having a single nozzle array. In this embodiment each of the two structures can physically be similar to heads 21a and 21b.
In a preferred embodiment, there are M model heads each having m arrays of p nozzles, and S support heads each having s arrays of q nozzles such that M.times.m.times.p=S.times.s.times.q. Each of the M.times.m modeling arrays and S.times.s support arrays can be manufactured as a separate physical unit, which can be assembled and disassembled from the group of arrays. In this embodiment, each such array optionally and preferably comprises a temperature control unit and a material level sensor of its own, and receives an individually controlled voltage for its operation.
One configuration in which one support material head 21c and two modeling material heads 21a, 21b are employed is illustrated in FIG. 1d. In this configuration, the number of nozzle arrays in the support head is twice the number of nozzle arrays in each modeling head, but the overall number of nozzle arrays designated to dispense support material equals the overall number of nozzle arrays designated to dispense modeling material. When all nozzle arrays are characterized by the same dispensing rate, this embodiment corresponds to a=1, and when the nozzle arrays of head 21c are characterized by a dispensing rate which differ from the dispensing rate of the nozzle arrays of each of heads 21a and 21c, this embodiment corresponds to a.noteq.1.
In various exemplary embodiments of the invention system 10 has at least two operation modes: in a first operation mode all modeling material heads operate, preferably at the same dispensing rate, during a building scan cycle, namely, all nozzles are operative throughout the building scan cycle in every location of the object layer. Since the different heads are not necessarily located in the same place (e.g., they can be located one after the other in the scanning direction), there is a certain time delay between each of the heads and nozzle rows. The term "location of the layer" refers to a small collection of pixels in the X-Y plane.
The system of the present embodiments enables selection of modeling materials from a given number of modeling materials and/or materials intended to comprise part of the object being fabricated, to define desired combinations of the selected materials and define the `spatial location` of their deposition (combined or separate) within the layer, thus enabling the formation of a broad range of materials (i.e., material combinations), having a broad range of material attributes or properties, and enabling the fabrication of an object which may consist of multiple different combinations of modeling materials, in different parts of the object, according to the properties desired to characterize each part of the object.
As aforesaid, the first operation mode can be selected either for fabricating objects using a modeling material from a single material container, or for fabricating objects made of a uniform mix from different modeling material containers. The relative amount of the ith modeling material is preferably Ni/m where m is the number of modeling heads and Ni is the number of heads that receive the i-th modeling material. A cross-sectional view of two objects, which are simultaneously fabricated on tray 30 according to a preferred embodiment of the present invention from a single modeling material 140a is illustrated in FIG. 2a.
The second operation mode is preferably selected when it is desired to fabricate objects using different modeling materials and/or different combinations of modeling materials in different regions, or when a single scan cycle is used to simultaneously fabricate layers of different objects with different modeling materials and/or material combinations on the same working surface. A cross sectional view of two objects, which are simultaneously fabricated on tray 30 from three different modeling materials 140a, 140b and 140c, according to a preferred embodiment of the present invention, each occupying a distinct region, is illustrated in FIG. 2b.
In one embodiment of the invention, two or more modeling materials may be dispensed, where one or both of the materials may not have the properties required to allow the building of the desired object. The combination of the two materials can provide a functional modeling material. For example, one of the materials may not solidify during the fabrication process, but remain in liquid, gel, paste or other non-solid or semi-solid form, while the other material does solidify during the fabrication process. The solidified material can "contain" the non-solidified material, or, alternatively, the non-solidified material can be drained, burnt out or otherwise removed once the process is complete so as to provide a model which is hollow or porous.
(iv) graphically depict the sorted combinations (see, e.g., Tables 1 and 2 below, in which M1-M10 represent materials or material combinations); and (v) provide the user with the option and ability to select one or more combinations and assign them to an article or part of an article to be built.
TABLE-US-00001 TABLE 1 Rigid HDT 60 M4 50 M1 40 M2 30 20 10 M5 M3 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Elongation
For example, suppose that apparatus 14 comprises N modeling material heads (N.gtoreq.2) each capable of dispensing modeling material at certain maximal rate. According to a preferred embodiment of the present invention the overall throughput of apparatus 14 when the same modeling material is supplied to all dispensing heads is N times larger (i.e., at least to times larger) than the overall throughput when a different modeling material is supplied to each dispensing head. Control unit 52 preferably controls the modeling material dispensing heads and the support material dispensing heads such as to maintain a predetermined ratio between the amounts of modeling material and support material for each layer.
As used herein the term "generally similar", when used in conjunction to a miserable quantity (such as dispensing rate) refers to the same .+-.10%.
Reference is now made to FIGS. 3a-c and 4a-c, which are fragmentary schematic illustrations of a supply apparatus 50, according to various exemplary embodiments of the present invention. Apparatus 50 preferably comprises a plurality of containers 58 for holding the building materials. In the fragmentary illustration of FIGS. 3a-c and 4a-c there are two such containers 58a and 58b, for holding modeling materials to be supplied to dispensing heads 21a and 21b, but it is to be understood that apparatus 50 can comprise any number of containers, including one or more containers for holding support materials. Apparatus 50 further comprises a building material flow unit 60 arranged for selectively allowing flow of building materials to fabrication apparatus 14. More specifically, unit 60 selectively allows flow of materials to reservoirs 56a and 56b of dispensing heads 21a and 21b.
This can be achieved in more than one way. In the embodiments illustrated in FIGS. 3a-c, unit 60 comprises an arrangement of conduits 62, valves 64 and/or pumps 66. Each valve can assume an open state in which material is allowed to flow in the conduit at which the valve is introduced and a closed state, in which it does not allow flow of material therethrough. An open valve is illustrated in FIGS. 3a-c as a square and a closed valve is illustrated as a square filled with a cross.
Unit 60 can assume several states. FIG. 3a illustrates a state of unit 60 in which the valves at the exits of the containers are open but no mixing of materials is allowed. Thus, in this configuration, container 58a supplies material to reservoir 56a but not to reservoir 56b, and container 58b supplies material to reservoir 56b, but not to reservoir 56a. This configuration is useful in embodiments in which different heads dispense different materials (e.g., in the second operation mode, or in the first operation mode in which materials are mixed during their deposition).
FIG. 3b illustrates the same combination of valve states as in FIG. 3a, but with the same modeling material in both containers. This embodiment is useful in the first operation mode whereby all heads dispense the same material.
FIG. 3c illustrates a state of unit 60 in which the valve at the exit container 58a is closed, the valve at the exit of container 58b is open, and the valves on conduits which allow flow of material from container 58b to reservoirs 56a and 56b are open. Thus, in this configuration, container 58a does not supply material, and container 58b supplies material to both reservoirs 56a and 56b. This embodiment is also useful in the first operation mode.
FIGS. 4a-c illustrate an embodiment in which unit 60 comprises an arrangements of conduits 62 and pumps 66.
Each pump can assume an operative state in which it generates flow of material and a non-operative state in which it does not allow flow of material. An operative pump is illustrated in FIGS. 4a-c as a circle with circular arrow, and a non-operative pump is illustrated in FIGS. 4a-c as an empty circle.
FIG. 4a illustrates a state of unit 60 in which the pumps generate flow of material from container 58a to reservoir 56a but not to reservoir 56b, and flow of material from container 58b to reservoir 56b but not to reservoir 56a. This configuration is useful in embodiments in which different heads dispense different materials (e.g., in the second operation mode, or in the first operation mode in which materials are mixed during their deposition).
FIG. 4b illustrates the same combination of pump states as in FIG. 4a, but with the same modeling material in both containers. This embodiment is useful in the first operation mode whereby all heads dispense the same material.
FIG. 4c illustrates a state of unit 60 in which the pumps at the exit of container 58a are not operative, but the pumps at the exit of container 58b are operative, such that container 58a does not supply material, and container 58b supplies material to both reservoirs 56a and 56b. This embodiment is also useful in the first operation mode.
Also contemplated are different combinations of the above states. For example, when there are four modeling heads, unit 60 can assume the state as illustrated in FIG. 3b or 4b for two heads and the state as illustrated in FIG. 3c or 4c for the other two heads, thus allowing flow of materials from three containers to four heads.
In the former case (the first operation mode) all the heads are operative throughout the scan cycle, and are fed by the same modeling material or materials. This can be achieved, for example, using the combination of valve states illustrated in FIG. 3b-c or the combination of pump states illustrated in FIGS. 4b-c. In the embodiment in which all the containers of apparatus 50 hold the same modeling material (e.g., FIGS. 3b and 4b), the scan cycle is preferably preceded by a step in which containers holding other modeling materials are replaced. Additionally, reservoirs and conduits filled with other modeling materials are preferably emptied, e.g., by performing one or more purging cycles, before commencing or continuing the fabrication step. If so required, unit 52 can adjust the applied voltage and/or temperature in the respective reservoirs. In the embodiment in which one or more containers supply the modeling material to all the heads (e.g., FIGS. 3c and 4c), the scan cycle is preferably preceded only with purging cycles and optionally voltage and temperature adjustments, without replacement of containers.
Thus, according to the presently preferred embodiment of the invention unit 60 assumes the state in which different containers supply different building materials to different dispensing heads (e.g., as illustrated in FIG. 3a or 4a). In the first operation mode, where all heads operate during the scan cycle, all heads may be fed by the same containers, or all containers may contain the same material. In multiple modeling material mode, each modeling material is dispensed from a different head, each head being supplied by a different container, and the dispensed materials are optionally mixed or interspersed amongst each other, upon contacting the working surface.
In some cases a layer made of a mixture of different modeling materials at uneven, but predetermined mix ratio can be obtained in the first operation mode, either by introducing the same modeling material to more than one container, or by selecting the state of unit 60 such that one or each of several modeling material containers supplies material to more than one modeling heads. A representative example is shown in FIG. 5, which is a schematic illustration of supply apparatus 50 and heads 21 in an embodiment in which there are four modeling heads 21a-d having the same dispensing rate, and one support head 21e with a dispensing rate which is four times the dispensing rate of a model head. The dispensing rates of heads 21a-d are represented in FIG. 5 by two nozzle arrays 22 per head, and dispensing rate of head 21e is represented by eight nozzle arrays 22.
Reference is now made to FIG. 6 which schematically illustrates the registration of the nozzle arrays of the various heads along the indexing direction Y, according to various exemplary embodiments of the present invention. Shown in FIG. 6 are three nozzle arrays 22a-c each designated to dispense a different modeling material, and three nozzle arrays 42a-c designated to dispense support material. In the present example, each array includes 9 nozzles, uniformly distributed along the indexing direction Y. Other numbers of nozzles per array are not excluded from the scope of the present invention. Nozzle arrays 22a-c and 42a-c can correspond to four different dispensing heads, three modeling heads each having one of arrays 22a-c, and one support head having all three arrays 42a-c. But this need not necessarily be the case. For example, nozzle arrays 22a-c and 42a-c can correspond to six different dispensing heads (three modeling heads and three support heads), two different dispensing heads (one modeling head and one support head), or any other combination.
According to a preferred embodiment of the present invention, the nozzle arrays are aligned along the scanning direction X in a manner such that a plurality of rows of modeling material are formed on the working surface in a substantially uniform distribution along the indexing direction Y. In other words, when all arrays operate during a single scan, there is a generally similar distance, d, between every two successive rows. In various exemplary embodiments of the invention, the nozzle arrays of support material (arrays 42a-c in the representative example of FIG. 6) are disposed along the indexing direction Y such that nozzles of each nozzle array of support material are aligned along the scanning direction X with nozzles of one nozzle array of modeling material. In the present example, the nozzles of array 42a are preferably aligned with the nozzles of array 22a, the nozzles of array 42b are preferably aligned with the nozzles of array 22b and the nozzles of array 42c are preferably aligned with the nozzles of array 22c.
For a plurality of head arrays, the arrays are preferably configured in sequential manner with respect to the scanning direction X (one behind the other) at locations denoted by integer numerals from 1 to N, where N is the number of arrays (three in the present example). The arrays are registered in an interlaced fashion in the indexing direction. Hence, when there are M nozzles (nine in the present example) in each array, a single scan in which all heads operate results in the formation of N.times.M rows (27 rows in the present example). Formation of N.times.M rows using a single modeling array and a single support array, on the other hand, requires a cycle of N scans (three in the present example), with intermediate shifts of the arrays along the indexing direction.
When N, the total number of arrays designated for dispensing modeling material, is an integer power of 2 (i.e., N=2, 4, 8, . . . ), such that, for any positive integer K.ltoreq.N, lines of modeling material formed by nozzle array K are symmetrically disposed between lines of modeling material formed by all nozzle arrays of at locations 1 to K-1.
The situation is exemplified in FIG. 7 which schematically illustrates the registration of the nozzle arrays along the indexing direction, in a preferred embodiment in which N=4. Shown in FIG. 7 are four nozzle arrays 22a-d each designated to dispense a different modeling material, and four nozzle arrays 42a-d designated to dispense support material. Similarly to the example illustrated in FIG. 6, each array in the present example includes 9 nozzles, uniformly distributed along the indexing direction Y. Yet, as stated, other numbers of nozzles per array are not excluded from the scope of the present invention. Nozzle arrays 22a-d and 42a-d can correspond to any combination of modeling heads and support heads, as explained above in conjunction with FIG. 6. The nozzles of arrays 42a-d are respectively aligned along the indexing direction with the nozzles of arrays 22a-d.
In the exemplified configuration illustrated in FIG. 7, the four arrays 22a, 22b, 22c and 22d are arranged with respect to the scanning direction X in sequential order at locations 1, 2, 3 and 4 respectively. The alignment along the indexing direction is such that lines of modeling material formed by the nozzle array at location 2 (array 22b in the present example) are symmetrically disposed between lines of modeling material formed by the nozzle arrays at location 1 (array 22a in the present example). Lines of modeling material formed by the nozzle array at location 3 (array 22c in the present example) are symmetrically disposed between lines of modeling material formed by the nozzle arrays at locations 1 and 2 (arrays 22a 22b in the present example); and lines of modeling material formed by the nozzle array at location 4 (array 22d in the present example) are also symmetrically disposed between lines of modeling material formed by all nozzle arrays of at locations land 2 (arrays 22a and 22b in the present example).
The advantage of using such symmetry is that it prevents or reduces `sticking` of adjacent lines to each other, and formation of asymmetrical gaps between adjacent lines. If a new line of modeling material is deposited between two formerly deposited lines, but closer to one than to the other, it will stick to or merge with the closer line and not with the line on its other side causing uneven layer thickness and formation of asymmetrical grooves between adjacent lines.
In various exemplary embodiments of the invention the rescaling factors also depend on the type or types of modeling material used to fabricate the layer. This is because different materials may have different contraction characteristic after being cured and cooled. Thus, regions or objects having different modeling materials are preferably resealed according to a different rescaling factor. Alternatively, objects that are formed of different modeling materials in different distinct regions (cf. FIG. 2b) the rescaling factor can be according to the hardest material in the fabricated object. For layers or objects formed from mixture of modeling materials, the scale factor is preferably a weighted average of the constituent modeling materials forming the mixture.
Reference is now made to FIG. 8, which is a schematic illustration of a cross sectional view of an object 70 having a continuous buffer layer 76 located near the object's surface. The interior 72 of object 70 is made of a generally hard modeling material which is being surrounded by buffer layer 76 of an elastic material. Elastic layer 76 is surrounded by an additional continuous layer 78 of a hard modeling material, which, in the representative illustration of FIG. 8 is the outer layer of object 70. Each of layers 76 and 78 is preferably thinner than interior 72, but can be made of one or more sub-layers of modeling material. A typical thickness of layers 76 and 78 is about 100 .mu.m. It is to be understood that object 70 can also comprise other internal or external structures which may be continuous or discontinuous. Two adjacent structures can be made of different materials.
A representative example of a deep pattern is illustrated in FIG. 10a, which illustrates an X-Z cross section of the object. The fabrication process is preferably as follows: a first layer of building material of uniform thickness is formed on a work surface according to a given multi material pattern. Subsequent layers, successively elevated in the Z direction, are built one on another, each depicting the same pattern as depicted in the first layer. The material combinations in the layer can be, for example, an appropriate mix of basic color materials (that are supplied to the machine heads). In this way the same color pattern appears at both the bottom of the object and at its top surface.
In another embodiment, illustrated in FIG. 10b, which illustrates an X-Z cross section of the object, image information of the deep pattern can be combined with image information of another three-dimensional object in a manner such that only common parts of the deep pattern and three-dimensional object are fabricated by the solid freeform fabrication. In other words, when the deep pattern is fabricated, its surface is trimmed according to the outer surface of the three-dimensional object.
According to an additional embodiment of the present invention, there is provided a method in which at least two separate objects are fabricated by solid freeform fabrication on a building tray. The separate objects are fabricated from different modeling material combinations. According to the present embodiment of the invention, the dimensions of the objects are rescaled along a direction so as to compensate for post-formation shrinkage of the objects along the direction. The scale factors of the different can be different. Regions having different modeling material combinations that touch each other can be rescaled according to a common resealing factor.
In the present Example, an object is defined as a volume in space (usually specified in an X, Y, Z coordinate system) which is confined by one or more close surfaces which do not intersect with each other (see, e.g., FIG. 2a). A region in the object is a sub-volume of the object which is confined in one or more close surfaces which do not intersect with each other (see, e.g., FIG. 2b).
The computer can comprise a display device which displays the material characteristics (e.g., mechanical characteristics, thermo-mechanical characteristics, optical characteristics, etc.) of each of the N input materials and optionally each possible combination of materials. Thus, for example, when there are G groups of combinable input materials (G.ltoreq.2.sup.N-N-1), the computer can display the characteristics of up to N+G different materials and material combinations.
Table 3 can be used to define an elementary three-dimensional body whose dimensions include a width parameter along each of the three X-Y-Z Cartesian coordinates. For example, for a (0.1 mm).times.(0.1 mm).times.(0.1 mm) cube, the values in the first row of Table 3 are: width (X)=width (Y)=width (Z)=0.1 mm.
The second row of Table 3 can be used to define the distance between adjacent elementary three-dimensional bodies. This is conveniently done using a space parameter along each of the three X-Y-Z Cartesian coordinates. For example, when width (X)=width (Y)=width (Z)=0.1 mm, and space (X)=space (Y)=space (z)=0.2 mm, Table 3 defines a composite material wherein 0.1.times.0.1.times.0.1 cubes of a material are uniformly distributed in a second material, and wherein the distance between the cubes along each of the X, Y and Z axes equals 0.2 mm.
In some embodiments of the present invention one or more additional parameters is added to Table 3 so as to increase the possibilities available in the composite material definition process. These additional parameters can include "thickness" and "offset". For example, when the thickness parameter is defined as thickness=1 mm and the XY "offset" as offset=0.05 mm, the bitmap defined by the Table 3 is first built up to a 1 mm height (thickness). Then, the same bitmap is built offset a distance of 0.05 mm from the first bitmap's axes, up to a 1 mm further height, at which point the bitmap returns to the former position and so on, alternating between the two positions offset from one another until the entire three-dimensional structure has been built.
The Boolean comparison between the composite material defined by each bitmap and the bitmaps defining different three-dimensional object cross-sections enables the building of a three-dimensional object using a composite material. For example, comparing the bitmap defined Table 4 below and the bitmaps which define the cross sections of a (50 mm).times.(50 mm).times.(50 mm) cube results in a cube sequentially made of a composite material as schematically shown in FIG. 11.
The values introduced in Tables 5-A and 5-B can be graphically presented as bitmap, as illustrated in FIGS. 12a and 12b, respectively. (ii) Laminate (XY) Model Structure
The values introduced in Tables 6-A and 6-B can be graphically presented as bitmap, as schematically illustrated in FIGS. 13a-b, respectively. Interpenetrating Network (IPN) Model Structure
Reference is now made to FIGS. 21a-b, which are schematic illustrations of a side view (FIG. 21a) and a top view (FIG. 21b) of a combined printing device 200, according to various exemplary embodiments of the present invention. Combined printing device 200 comprises a printing assembly 202 having a plurality of printing units 218, and a service assembly 204 having a plurality of service stations 216. At least one of the two assemblies 202 and 204, preferably printing assembly 202 is movable, and in any event a relative motion can be established between printing assembly 202 and service assembly 204.
An additional service task which can be executed while docking is the replacement of an active printing element. A technique for performing such replacement, according to some embodiments of the present invention is illustrated in FIG. 21b. Suppose that a particular printing unit, designated by reference sign 218a, is to be replaced, and that assembly 202 docks such that unit 218a is near (e.g., opposite to) a particular service station, designated by reference sign 216a. Suppose further that a replacement printing unit, designated by reference sign 218b, is mounted on another service station, designated by reference sign 216b, which is away from unit 218a. Firstly, unit 230 signals service station 216a to disconnect unit 218a from assembly 202. In response to the signal, actuator unit 220 of station 216a disconnects unit 218a and mounts it on station 216a (e.g., via a holder 224a). for example, using an installed in station 216a). As a result, the holder 215 (not shown) which held unit 218a on assembly 202 becomes vacant. Secondly, unit 230 signals assembly 202 to maneuver and dock such that that the vacant holder of assembly 202 is near service station 216b of assembly 204. Thirdly, unit 230 signals service station 216b to connect unit 218b to assembly 202. In response to the signal, actuator unit 220 of station 216b disconnects unit 218b from assembly 204 and mounts it on the vacant holder of assembly 202.
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