U.S. patent application number 10/634570 was filed with the patent office on 2004-02-26 for three dimensional object and method of making the same.
This patent application is currently assigned to Milwaukee School of Engineering. Invention is credited to Crockett, Robert S., Gervasi, Vito R..
Application Number | 20040039470 10/634570 |
Document ID | / |
Family ID | 28044317 |
Filed Date | 2004-02-26 |
United States Patent
Application |
20040039470 |
Kind Code |
A1 |
Gervasi, Vito R. ; et
al. |
February 26, 2004 |
Three dimensional object and method of making the same
Abstract
A three dimensional object having a first one-piece build style
lattice including a plurality of substantially uniform build style
units and a second one-piece build style lattice integrally formed
with and interlaced with the first lattice, the second lattice
including a plurality of substantially uniform build style
units.
Inventors: |
Gervasi, Vito R.; (New
Berlin, WI) ; Crockett, Robert S.; (Shell Beach,
CA) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH, LLP
100 E WISCONSIN AVENUE
MILWAUKEE
WI
53202
US
|
Assignee: |
Milwaukee School of
Engineering
Milwaukee
WI
|
Family ID: |
28044317 |
Appl. No.: |
10/634570 |
Filed: |
August 5, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10634570 |
Aug 5, 2003 |
|
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|
09633314 |
Aug 7, 2000 |
|
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6623687 |
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60147691 |
Aug 6, 1999 |
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Current U.S.
Class: |
700/119 ;
264/401 |
Current CPC
Class: |
F28F 21/06 20130101;
B29C 64/40 20170801; F28F 7/02 20130101; B29C 64/135 20170801; F28F
2210/02 20130101; B29C 45/7312 20130101; B33Y 50/00 20141201; F28D
2021/0078 20130101; B29C 2045/7362 20130101 |
Class at
Publication: |
700/119 ;
264/401 |
International
Class: |
G06F 019/00 |
Claims
1. A method for forming a three dimensional object, said method
comprising the steps of: generating a digital representation of the
object; generating a digital representation of a first build style
lattice having a predetermined, substantially uniform structure;
generating a digital representation of a second build style lattice
having a structure similar to the first build style lattice;
overlaying the respective representations of the object, the first
build style lattice and the second build style lattice;
intersecting the overlaid representations to generate a digital
representation of the object incorporating the first build style
lattice and the second build style lattice; and fabricating the
digital representation of the object.
2. The method set forth in claim 1 wherein the fabricating step
includes providing first material for the first lattice and a
second material for the second lattice.
3. The method set forth in claim 1 wherein the overlaying step
includes shifting the position of the second build style lattice
relative to the first build style lattice to interlace the first
and second build style lattices.
4. The method set forth in claim 1 wherein the first build style
lattice includes a plurality of interconnected legs and nodes.
5. The method set forth in claim 4 wherein the legs of the first
build style lattice have a substantially uniform thickness.
6. The method set forth in claim 4 wherein the second build style
lattice includes a second plurality of interconnected legs and
nodes having a substantially uniform thickness different from the
thickness of the legs of first lattice.
7. The method set forth in claim 6 wherein the object has a first
region and a second region, wherein said first and second build
style lattices extend into the first region and the second region
and wherein the thickness of the legs of the first lattice and the
thickness of the legs of the second lattice vary from the first
region to the second region.
8. The method set forth in claim 7 wherein the thickness of the
legs of the first build style lattice and the thickness of the legs
of the second build style lattice vary inversely from the first
region to the second region.
9. The method set forth in claim 1 wherein the first and second
build style lattices are interlaced and define therebetween an
interface.
10. The method set forth in claim 9 wherein the interface is
substantially hollow.
11. The method set forth in claim 9 wherein the interface is
occupied by a fluid.
12. The method set forth in claim 8 wherein the interface defines
at least one channel for conducting a fluid along a predetermined
path.
13. The method set forth in claim 8 wherein the interface is
occupied by a solid material.
14. The method set forth in claim 13 wherein the interface is
occupied by the legs of the first and second build style
lattices.
15. The method set forth in claim 1 wherein the step of generating
a digital representation of the object includes generating a
representation of a boundary skin and wherein the fabricating step
includes fabricating the boundary skin so that the first build
style lattice supports the skin.
16. The method set forth in claim 1 wherein the second build style
lattice supports the skin.
17. The method set forth in claim 4 wherein the legs of the first
lattice are hollow and are interconnected.
18. The method set forth in claim 1 wherein the legs of the first
build style lattice define respective bores having an inner
diameter and wherein the inner diameters of the bores vary to form
at least one capillary.
19. The method set forth in claim 1 wherein the step of generating
a digital representation of the first build style lattice includes
generating a representation of a plurality of legs and wherein the
fabricating step includes fabricating at least one of the plurality
of legs so as to be hollow.
20. The method set forth in claim 19 wherein the step of generating
a digital representation of the first build style includes the step
of generating a digital representation of a third build style
lattice, the overlaying step includes overlaying the digital
representations of the first and third build styles and the
intersecting step includes intersecting the digital representations
of the first and third build styles to result in the representation
of hollow legs in the first build style lattice.
21. A three dimensional object comprising: a first one-piece build
style lattice including a plurality of substantially uniform build
style units; and a second one-piece build style lattice integrally
formed with and interlaced with the first lattice, the second
lattice including a plurality of substantially uniform build style
units.
22. The object set forth in claim 21 wherein the first lattice is
made of a first material and the second build style lattice is made
of a second material.
23. The object set forth in claim 21 wherein the first build style
lattice includes a plurality of interconnected legs and nodes.
24. The object set forth in claim 23 wherein the legs of the first
build style lattice have a substantially uniform thickness.
25. The object set forth in claim 24 wherein the second build style
lattice includes a second plurality of interconnected legs and
nodes having a substantially uniform thickness different from the
thickness of the legs of first lattice.
26. The object set forth in claim 25 wherein the object has a first
region and a second region, wherein said first and second build
style lattices extend into the first region and the second region,
and wherein the thickness of the legs of the first lattice and the
thickness of the legs of the second lattice vary from the first
region to the second region.
27. The object set forth in claim 26 wherein the thickness of the
legs of the first build style lattice and the thickness of the legs
of the second build style lattice vary inversely from the first
region to the second region.
28. The object set forth in claim 21 wherein the first and second
build style lattices define therebetween an interface.
29. The object set forth in claim 28 wherein the interface is
substantially hollow.
30. The object set forth in claim 29 wherein the interface is
occupied by a fluid.
31. The object set forth in claim 28 wherein the interface defines
at least one channel for conducting a fluid along a predetermined
path.
32. The object set forth in claim 31 wherein the channel has a
cross-section which narrows to define a capillary.
33. The object set forth in claim 28 wherein the interface is
occupied by a solid material.
34. The object set forth in claim 33 wherein the interface is
occupied by the legs of the first and second build style
lattices.
35. The object set forth in claim 21 wherein the object includes a
boundary skin and wherein the first build style lattice supports
the skin.
36. The object set forth in claim 35 wherein the second build style
lattice supports the boundary skin.
37. The object set forth in claim 23 wherein the legs of the first
lattice are hollow.
38. The object set forth in claim 37 wherein the legs of the first
build style lattice define respective bores having an inner
diameter and wherein the inner diameters of the bores vary to form
at least one capillary.
39. The object set forth in claim 37 and further including a
boundary skin supported by at least one of the first and second
build style lattices.
40. A three dimensional object formed through use of a free form
fabrication method comprising the steps of: generating a digital
representation of the object including a representation of a
surface of the object; generating a digital representation of a
first build style lattice having a predetermined, substantially
uniform structure; generating a digital representation of a second
build style lattice having a structure similar to the first build
style lattice; intersecting the overlaid representations to
generate a digital representation of the object incorporating the
first and second build style lattices; and fabricating the digital
representation of the object incorporating the first and second
build style lattices to form a boundary skin, a first lattice
integrally formed with and extending from the skin and a second
lattice interlaced with the first lattice and integrally formed
with and extending from the skin.
Description
RELATED APPLICATIONS
[0001] This application claims priority to the filing date of
provisional application Serial No. 60/147,691 filed Aug. 6,
1999.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates to techniques for making three
dimensional objects, and particularly to solid freeform fabrication
techniques and objects made through use of such techniques.
[0004] 2. Related Prior Art
[0005] Solid Freeform Fabrication ("SFF") or rapid prototyping
techniques are typically useful for quickly making complex or
simple three dimensional objects. In general, SFF processes enable
rapid and accurate fabrication of three dimensional objects which
otherwise could be produced only by lengthy molding and machining
processes. SFF techniques are, generally speaking, additive
processes whereby the object to be formed is fabricated by reducing
a model or representation of the object's ultimate configuration
into a series of planar cross-sections and subsequently recompiling
the cross-sections to reconstruct the object.
[0006] Stereolithography is one of several known SFF techniques. In
practicing this process using equipment commonly known as
stereolithography apparatus ("SLA"), an ultraviolet laser beam
selectively scans a reservoir of a of photosensitive liquid along a
predetermined path. Upon the laser beam being exposed to the
portions of the liquid lying in the beam's path, the exposed
portions of the liquid cure or solidify through polymerization. An
example of stereolithographic methods and equipment are disclosed
in U.S. Pat. No. 5,256,340, which issued to Allison on Oct. 26,
1993 and which is assigned to 3D Systems, Inc.
[0007] Another known SFF process utilizes Cubital's Solider system.
In general, this process utilizes a photo-mask which represents the
image of the particular layer of the object to be produced. The
mask is positioned over a layer of photosensitive liquid. Selective
solidification of the layer occurs upon exposure of ultraviolet
light through the mask. Unsolidified resin is drained from the
partially composed object leaving the desired configuration of
surfaces and cavities. The cavities of the object are then filled
with a liquid material having a relatively low melting point, such
as wax. Upon solidification of the wax, the uppermost layer of the
object is made uniform, such as by planing or milling. Then a new
layer of the photocurable liquid is positioned on the surface.
Another mask is created and the process is repeated. Upon
completion of production, the wax is melted and pour from the
object to expose the configuration of the object. As discussed
below, the object may comprise a plurality of interconnected,
internal cavities or may be hollow.
[0008] In addition to these specifically described SFF techniques,
there are other techniques not described in detail here. Among
these techniques are plasma deposition techniques whereby plasma is
deposited along a predetermined path and permitted to solidify to
build an object on a layer by layer basis. One such additive
technique is known as Laser Engineered Net Shaping (LENS.TM.)
technology developed by Optomec, Inc., located in Albuquerque, N.
Mex. The Optomec Directed Materials Deposition process uses a high
power laser focused onto a substrate to melt the substrate surface.
Metal powder is then blown into the melt pool to increase its
volume. Subsequent scanning of the substrate relative to the laser
beam provides a means to deposit thin metal lines on the substrate
surface. With the addition of computer control, the Optomec system
deposits the metal lines to form patterns on the substrate surface.
Finally, this patterning method is coupled with the ability to
interpret 3-D CAD designs and allows those patterns to represent a
series of slices through the part from the CAD system. Using this
method, a component can be fabricated directly from a CAD solid
model one layer at a time until the entire object is realized. The
result is fully dense metal parts with dimensional accuracy.
[0009] Solid Freeform Fabrication technologies depend on the use of
computers to generate cross-sectional patterns representing the
layers of the object being formed, and generally require the
associated use of a computer and computer-aided design and
manufacture (CAD/CAM) software. In general, these techniques rely
on the provision of a digital representation of the object to be
formed. The digital representation of the object is reduced or
"sliced" to a series of cross-sectional layers which can be
overlaid to form the object as a whole. The SLA or other apparatus
for carrying out the fabrication of the object then utilizes the
cross-sectional representations of the object for building the
object on a layer-by-layer basis by, for example, determining the
path of the laser beam in an SLA or the configuration of the mask
to be used to selectively expose UV light to photosensitive
liquids.
[0010] It is also known to form hollow structures wherein just the
periphery or boundary skin of the object is formed. However,
fabrication of entirely hollow objects sometimes is not acceptable
because of limitations in the resultant structure and the
photosensitive materials used by SLA. In particular, hollow
structures fabricated by utilizing only a boundary skin often
suffer from high structural stresses, shrinkage, curl in the
materials and other distortions of the object.
[0011] It is also known to form the periphery of the object by
formation of a substantially intact boundary skin, and to provide
an integrally formed lattice located internally within the skin
boundary. An example of such a technique or "build style" is the
QuickCast.TM. system by 3D Systems, Inc. which can be used to
produce three dimensional objects having a skin and a
honeycomb-like internal structure or lattice extending between the
boundaries defined by the skin.
[0012] The desired internal and external object geometry depends
upon the anticipated usage of the object to be formed and is based
upon a computer generated model or representation of the object.
For example, it may be desirable to produce an object with a hollow
portions, solid portions and portions occupied by a lattice work.
These "build styles" each have distinct advantages and
disadvantages. For example, certain build styles, such as the
QuickCast.TM. build styles can be useful when the resultant object
is to be filled with a material to solidify, strengthen or
otherwise further process the object. The presence of a lattice
build style can often afford more ready introduction of
strengthening materials into the object, can provide dimensional
stability, dimensional accuracy and functionality, or provide a
more accurate model.
SUMMARY OF THE INVENTION
[0013] While it is thus generally known to use SFF processes
utilizing a single lattice build style to make a three-dimensional
object, such techniques and the resultant objects still have
significant practical limitations. In particular, the materials
used in some SFF techniques, such as photosensitive resins used in
an SLA have physical characteristics which limit the usefulness of
the resultant object. Among the features of the present invention
is the enhancement of known SFF techniques to include multiple
build style lattices in both the process of making the object and
in the resultant object itself. In one embodiment, the invention
provides an object that includes the structure of a first lattice
build style which is integrally formed as a single piece. The
object also includes a second lattice build style that is also
integrally formed in a single piece and that is intertwined or
interlaced with the structure of the first build style lattice. The
respective structures of the first and second build style lattices
are complementary and are sized and shaped to provide a resultant
object having advantageous characteristics and utility.
[0014] In this regard, the multiple lattice build styles can be
made in conjunction with a boundary skin layer to define the object
being made. When multiple lattice build styles are constructed
according to the present invention, advantageous results can be
achieved that are unavailable using known SFF techniques. For
example, interlaced lattice build styles can be used to form
entirely solid objects as well as objects having solid regions and
passages adjacent or extending through the solid regions. Such
structures can be made either with or without a boundary skin on
the object, and can provide passageways extending in close
proximity to the boundary skin. By utilizing interlaced lattice
build styles, objects having utility can be formed. For example,
heat exchangers, gradient material components, stress relief
structures and the like can be formed.
[0015] In one embodiment, the invention provides a three
dimensional object including a first one-piece build style lattice
including a plurality of substantially uniform build style units.
The object also includes a second one-piece build style lattice
integrally formed with and interlaced with the first lattice, the
second lattice including a plurality of substantially uniform build
style units.
[0016] In another embodiment, the invention provides a method for
forming a three dimensional object including the steps of:
generating a digital representation of the object; generating a
digital representation of a first build style lattice having a
predetermined, substantially uniform structure; generating a
digital representation of a second build style lattice having a
structure similar to the first build style lattice; overlaying the
respective representations of the object, the first build style
lattice and the second build style lattice; intersecting the
overlaid representations to generate a digital representation of
the object incorporating the first build style lattice and the
second build style lattice; and fabricating the digital
representation of the object.
[0017] In another embodiment, the invention provides a three
dimensional object formed through use of a free form fabrication
method including the steps of: generating a digital representation
of the object including a representation of a surface of the
object; generating a digital representation of a first build style
lattice having a predetermined, substantially uniform structure;
generating a digital representation of a second build style lattice
having a structure similar to the first build style lattice;
intersecting the overlaid representations to generate a digital
representation of the object incorporating the first and second
build style lattices; and fabricating the digital representation of
the object incorporating the first and second build style lattices
to form a boundary skin, a first lattice integrally formed with and
extending from the skin and a second lattice interlaced with the
first lattice and integrally formed with and extending from the
skin.
[0018] Other features and advantages of the invention will become
apparent to those skilled in the art upon review of the following
detailed description, claims and drawings.
DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 illustrates an apparatus for carrying out the
invention.
[0020] FIG. 2 illustrates a three-dimensional object embodying the
invention.
[0021] FIG. 3 illustrates a second three-dimensional object
embodying the invention.
[0022] FIG. 4 illustrates a third three-dimensional object
embodying the invention.
[0023] FIG. 5 illustrates a fourth three-dimensional object
embodying the invention.
[0024] FIG. 6 illustrates a fifth three-dimensional object
embodying the invention.
[0025] FIG. 7 is a cross-sectional view taken along line 7-7 in
FIG. 6.
[0026] FIG. 8 is a cross-sectional view taken along line 8-8 in
FIG. 6.
[0027] FIG. 9 is a cross-sectional view taken along line 9-9 in
FIG. 6.
[0028] FIG. 10 illustrates a sixth three-dimensional object
embodying the invention.
[0029] FIG. 11 illustrates a seventh three-dimensional object
embodying the invention.
[0030] Before one embodiment of the invention is explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangements
of components set forth in the following description or illustrated
in the drawings. The invention is capable of other embodiments and
of being practiced or being carried out in various ways. Also, it
is to be understood that the phraseology and terminology used
herein is for the purpose of description and should not be regarded
as limiting.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] The drawings illustrate apparatus 10 which can be used to
carry out the invention and objects embodying the invention. In
particular, and with initial reference to FIG. 1, the apparatus 10
is a stereolithography apparatus ("SLA") including a computer 14, a
laser beam generator 18 and a control 22 associated with the
computer 14 and laser beam generator 18. The apparatus 10 also
includes a tank 26 which contains a reservoir 30 of photosensitive
liquid. A model support base 34 is located in the tank 26 and can
be selectively indexed vertically within the reservoir 30 of liquid
by means of an elevator apparatus (not shown). The apparatus 10
also includes a mirror assembly 38 supported in position relative
to the laser beam generator 18 to precisely direct a beam produced
by the generator 18 into the reservoir 30 of liquid. The mirror
assembly 38 also can be selectively repositioned in a precise
manner by a mirror control apparatus (not shown) to redirect the
beam along a predetermined path along the surface of the liquid
reservoir 30. Many suitable SLA are available and can be
successfully used for apparatus 10. A preferred SLA is made by 3D
Systems, Inc. (Model Nos. SLA-190, SLA-250 and SLA-500). Suitable
computers and software applications for use with such SLA include
workstations manufactured by Silicon Graphics (Models: Indigo
R4000; INDY PC and SC; Indigo X2, R4000 and R4400) and IRIX
software (Release 5.2 or higher). A preferred photosensitive
material for use in SFF fabrication of objects for prototyping and
casting is an epoxy resin sold under the name Cibatool XB5170 for
use with the SLA-190 and SLA-250 models and Cibatool 5180 for use
with the SLA-500. A suitable software application for operating the
SLA is also provided by 3D Systems, Inc. under the Quickcast.TM.
(QuickCast 1.1 Workstation Software).
[0032] The apparatus 10 can be used to fabricate a variety of three
dimensional objects, such as the object A shown in FIG. 2. The
object A has a complex configuration and includes a first one-piece
lattice build style 100. The first lattice build style 100 includes
a plurality of substantially uniform build style units 104. While
various configurations of the build style units can be successfully
used, in the illustrated embodiment of the first lattice build
style each build style unit is in the form of a tetrahedron having
four interconnected legs 108 extending from a single node 112. Such
a lattice build style 100 is referred to as "tetra lattice", and
the structure and methods for producing tetra lattice are set forth
in co-pending U.S. patent application No. 09/249,917 filed Feb. 12,
1999 which is incorporated herein by reference in its entirety. The
first build style lattice 100 thus includes a plurality of
interconnected legs and nodes. In object A illustrated in FIG. 2,
the legs 108 and nodes 112 of the first build style lattice 100
have a substantially uniform thickness. However, as explained below
and as illustrated in the other figures, the legs and nodes can
also be made to vary in any of several aspects.
[0033] Object A also includes a second lattice build style 120. The
second lattice build style 120 also includes a plurality of
substantially uniform build style units 124 which, in the
illustrated embodiment, are also tetra lattice tetrahedrons having
respective legs 128 and nodes 132. Both the first and second
lattices 100, 120 are formed by SFF processes to be one-piece
structures. The first and second build styles 100, 120 are arranged
relative to each other so that the respective legs 108, 128 and
nodes 112, 132 of the tetra lattice units 104, 124 are interlaced.
In particular, the first and second build styles 100, 120 are
arranged so that the nodes 132 of the second build style lattice
120 are off-set from the nodes 112 of the first lattice build style
to a position occupying a space located intermediate the nodes 112
of the first lattice build style 100. When so offset, the lattices
100, 120 are complementary in that the respective nodes 112, 132
are spaced apart and, the axes of the respective legs 108, 128
extending between the nodes 112, 132 are skew to one another. As
described below, however, the thicknesses of the legs 108, 128 can
be increased to close the spacings between the lattices and to form
an object having solid or nearly solid regions.
[0034] FIG. 3 illustrates an object B having a first lattice build
style 200 including a series of interconnected build style units
204 and a second lattice build style 208 including a build style
units 212. The object B has cubital build style units 204, 208
rather than tetra hedron units, but otherwise is structurally
similar to object A in that the lattices 200 and 208 are
interlaced. Objects A and B illustrate that many possible
variations of build style unit configurations can be used
successfully to form interlaced lattice build styles.
[0035] While objects A and B include first and second build styles
only, the configuration of the build styles can be varied, and the
object can be formed by incorporating one or more boundary skins.
For example, FIG. 4 illustrates another three dimensional object
embodying the invention. Object C includes first and second build
style lattices 300, 304, and also includes a boundary skin 308 with
which the first and second style lattices 300, 304 are integrally
formed and which is supported by at least one, and preferably both,
of the first and second build style lattices 300, 304. The boundary
skin 308 of object C is relatively thin, but can be made as thin or
thick as is desired for the particular geometry of the object C and
the anticipated use of the object C. A typical wall thickness can
be in the range of 0.010 inches to 0.55 inches.
[0036] Objects including intelaced first and second build style
lattices can be configured to be entirely solid, partially solid
and partially hollow, or almost entirely hollow. In particular, the
first and second interlaced lattice build styles define
therebetween an interface which, in some configurations, can
include voids or spaces between the respective lattices or, in
other configurations, can include the intersection of materials
that are part of the lattices. Some intertwined lattice
applications require a fine, minimal lattice volume with open
communication throughout the lattice void space or interface. Other
applications require a lattice interface wherein the voids defined
by the lattices are interconnected and afford fluid flow in a
controlled yet continuous manner. In other applications, the
lattices are defined by structures having leg widths that are large
relative to the spacing or offset between the lattice structures so
that the legs of the lattice structures occupy the interface and
form material that provide a substantially solid region of the
object. In the extreme, the entire object can be a single piece of
solid material provided by the lattice structures.
[0037] More particularly, in the object B shown in FIG. 3, the
interface 312 is substantially hollow because the spacing between
the first and second lattice build styles 200, 208 and the relative
thickness of the legs and nodes of the respective build styles is
such that the structural components of the build styles do not
entirely occupy the object B. In this type of object, the interface
312 can be evacuated or occupied by a fluid. Also, as further
explained below, in some applications for use of the object, the
interface can be configured to define at least one channel for
conducting a fluid along a predetermined path. In other
applications, the fluid conducting channel can provide a
cross-section which vanes, e.g., widens to accept greater
volumetric flows or narrows to define a capillary-like structure
useful for slowing volumetric flow rates and/or carrying out mass
transfer functions.
[0038] In other objects, for example object C, the interface is
substantially solid because the spacing between the first and
second lattice build styles and the relative thickness of the legs
and nodes of the respective build styles is such that the
structural components of the build styles intersect and entirely
occupy the interior space of the object. In this type of object,
the interface is occupied by a solid material and is defined by the
transition between the materials used for the first lattice build
style and the second lattice build style. In effect, the interface
is occupied by the respective legs and nodes of the first and
second build style lattices.
[0039] The nature of the interface of objects made with interlaced
lattice build styles can vary in three dimensions and at different
rates through the entire object so that any combination and/or
variation of hollow and solid interfaces can be achieved. This can
be established in a variety of ways, such as by increasing or
decreasing the thickness of the legs of both lattices at equal
rates. The legs and nodes of the build style lattices can also be
made to be of independently varying thickness. For example, as
shown in FIG. 3, in object A the legs 314 and nodes 316 of the
first build style lattice can be made to be of one size or
thickness and the second build style lattice 208 can be made to
include interconnected legs 320 and nodes 322 having a
substantially uniform thickness different from the thickness of the
legs and nodes of first lattice.
[0040] One application for intertwined lattice build styles is for
the fabrication of objects made of functionally gradient material.
Functionally gradient materials essentially fuse two materials
having different physical characteristics to form one hybrid
material, and their use in structural components results in the
possibility of forming a vast range of new engineering materials.
Using the intertwined lattice structures, gradient materials can be
produced to have varying properties within a single object or
mechanical component so as to handle a spectrum of application
requirements, without changing design geometry of the component. A
component made of a functionally gradient material, i.e., made from
a first material and a second material using intertwined lattice
structures, provide a continuous, integrated component having
regions that transition from one material to another through a
series of interstitial layers. This interlaced, seamless transition
of material properties is accomplished without distinctive,
typically planar, seams or interfaces which are subject to stress
concentrations and which are found with traditionally bonded
materials.
[0041] Functionally gradient material components or
three-dimensional objects made of functionally gradient material
can be fabricated using additive SFF processed to build interlaced
lattice build styles having regions which transform from one
material to another in an integrated, predictable and predetermined
manner. One technique that can be used to create functionally
gradient material objects, the spacings between lattice build style
units can be kept constant while the leg thickness is increased in
a controlled manner. This controlled increase in branch thickness
results in a proportional change in volume percentage of material
combinations. At the extreme, the volumetric percentage of the
respective materials used for the lattice build styles varies
inversely from nearly 100% of a first material and nearly 0% of a
second material to 100% of the second material and 0% of the first
material, at any rate and in any direction with the gradient
material object. By using interlaced lattice build styles made of
respective materials to form such functionally gradient material
objects, the transformation of the object can be three-dimensional
and mechanically inter-linked.
[0042] As shown in FIG. 5, the object D illustrates an example of
an object that can be made using interlaced lattice build styles to
form a component having a functionally gradient material. The
object has a first region 400 and a second region 404. The first
region 400 of the object D has materials providing the first region
with particular physical characteristic, and the second region has
differing physical characteristics. These differences in physical
characteristics are achieved by providing the object D with first
and second build style lattices 408, 412 which each extend into the
first region and into the second region. The thickness of the legs
416 of the first lattice 408 and the thickness of the legs 420 of
the second lattice 412 vary from the first region 400 to the second
region 404 to vary the amount of material respectively provided by
each build style lattice 408, 412 to the respective regions of the
object.
[0043] In the example illustrated by FIG. 5, the thickness of the
legs 416 of the first build style lattice 408 and the thickness of
the legs 420 of the second build style lattice 412 vary inversely
from the first region 400 to the second region 404 so that the
percentage of material provided by the first build style lattice
408 varies from an upper threshold percentage in the first region
400 to a minimum percentage in the second region 404. Conversely,
the thickness of the legs 420 of the second build style lattice 412
vary to provide an upper threshold percentage in the second region
404 to a minimum percentage in the first region 400.
[0044] Other variations of the leg and node configurations are also
possible with interlaced lattice build styles. For example, in
object E shown in FIG. 6 (See, FIGS. 7, 8 and 9), the legs 500 and
nodes 502 of either of the build style lattices can be made to be
hollow and interconnected. More particularly, in the object E, the
legs of the first build style lattice define respective bores 510
having an inner diameter. The inner bores can be either uniform
along the length of the legs or the inner diameters of the bores
can vary to form capillary like structures (see bores 512 and 514
in FIGS. 8 and 9).
[0045] Such structures having hollow legs and nodes are useful in a
variety of applications. With the layer wise build method of SFF
arises the opportunity to produce cooling and heating systems
conformal to complex contoured surfaces, where heat exchange is
critical. Applications such as injection molding, where a large
percentage of cycle time is spent cooling, benefit significantly
from conformal cooling channels. Interlaced lattice build styles
can be used to make objects useful for conformal cooling and
heating.
[0046] In this case an object, such as object E in FIG. 6, having
interlaced lattice build styles to define a void adjacent a
boundary skin 520 is formed and used so that the inter-lattice
voids create the conformal fluid channels. Interconnections between
the lattice voids are useful to conduct fluids along flow paths 524
in close proximity to the boundary skin. An example of a use or
application of this type of object is a mold having a mold surface
and cooling channel adjacent the mold surface. The usage of
interlaced lattice build styles in such an application is
particularly useful for molds requiring deep mold cavities or in
molds having irregular contours on the mold surface. Also, the legs
of the respective interlaced lattices extend across the voids and
induce beneficial turbulence in the flow of fluids therethrough,
consequently resulting in improved convective heat transfer within
the object. In addition, to ensure even flow over a complex surface
or variable heat removal at various locations, node size or depth
of the interlaced lattice build styles can be adjusted throughout
the object.
[0047] Objects made with interlaced lattice build styles also can
be useful for mass transfer applications where entities, e.g.,
electrons, nutrients, etc., need to be moved efficiently from one
object to another in a controlled manner. The basic concept with
such transfer mechanisms is to intermesh interlaced lattice build
styles to form two distinctly separate structures or materials
separated by a thin wall. The two materials could be
liquid/gas/solid or conductive/insulative or any of a wide variety
of other possible combinations.
[0048] As one example, an object such as object E in FIG. 6, can be
used as a heat exchanger wherein a thermally conductive wall
separates two interlaced lattice build styles voids. The wall
transfers heat from one interlaced lattice build styles void fluid
to another. The Interlaced lattice build styles flow path is
non-linear and induces beneficial turbulent flow.
[0049] Another similar application is the use of the object as a
battery cell. In this application the wall separating the
interlaced lattice build style channels is a liquid electrolyte,
one interlaced lattice build styles is made of a solid material and
serves as the anode, and the other interlaced lattice build styles
is made of a solid material that serves as the cathode. Listed
below are other possible three dimensional objects including
interlaced lattice build styles and useful for transfer or
filtering systems:
[0050] dialysis (the wall is a semi-permeable membrane);
[0051] tissue engineering (the first interlaced lattice build style
form the artery, the second interlaced lattice build style forms
the vein, the wall become the cell growth zone as well as
capillaries);
[0052] circuitry (the first lattice is conductive, the second
lattice is conductive, and the interface is insulative);
[0053] filters/separation devices (the wall is a porous
material);
[0054] sensing (one fluid senses events in the other fluid through
the wall); and
[0055] fuel cells.
[0056] FIG. 10 illustrates an object F having a first lattice 800
providing a plurality of hollow legs and nodes, 804, 808 for
conducting a fluid (not shown). The lattice 800 is thus useful for
conducting a fluid such as air or oil. The ojbect F can be formed
to include an open lattice portion 812 through which a medium such
as air or a liquid or gas can pass, or can be made to include a
second interlaced lattice (not shown) including either hollow or
solid lattice members. The object F can be used for heat transfer
functions by conducting fluids within heat-transfer relation.
[0057] FIG. 11 illustrates another object G wherein the legs 900 of
lattice 902 and the legs 904 of a second lattice 906 diminish in
thickness as the lattices 902, 906 extend from one region 910 to a
second region 912 of the object G. As a consequence, the volume of
the interface 920 increases from region 910 to 920, thus forming
relatively large fluid paths or open lattice structure in region
912 and narrower fluid paths or capillary-like structure in region
910.
[0058] The objects A, B, C, D, E, F and G a can be fabricated so as
to have interlaced first and second build style lattices by use of
the apparatus 10 through the following steps. First, the
configuration of the object to be formed must be represented in
digital form using the computer 14. Among the variety of ways a
digital representation of the object can be provided is through use
of the computer 14 and associated CAD/CAM software resident on the
computer. A suitable CAD/CAM software application is sold under the
name ProEngineer by Parametrics Technologies Corporation, and a
suitable computer system to generate a digital representation of
the object to be formed is sold under the name Indigo by Silicon
Graphics. In the alternative, either the object itself or drawings
of the object can be digitized to provide a digital representation
of the object.
[0059] The next step in the fabrication method is generating a
digital representation of the first build style lattice having a
substantially uniform, build style structure 54. More particularly
in this regard, and with particular reference to FIG. 4, the
digital build style lattice includes a digital representation of
the above described tetrahedron lattice 54. The generation of a
digital representation of the lattice 54 is preferably performed
through use of aforementioned ProEngineer software application in
combination with software available from Materialize under the name
Magics RP.
[0060] The method also includes the step of generating a digital
representation of a second build style lattice having a structure
similar to the first build style lattice. In those applications
wherein the object being made includes a boundary skin, the step of
generating a digital representation of the object includes
generating a representation of a boundary skin. Similarly, in those
applications using the tetra lattice build style or other like
build style including, the step of generating a digital
representation of the first build style lattice includes generating
a representation of a plurality of legs and nodes.
[0061] The digital representations of the first and second lattices
can be generated in a variety of ways, and as explained above, can
incorporate legs having a variety of cross-sections and
configurations suitable for the object desired and for the intended
use of the object.
[0062] The next step in the fabrication method is overlaying the
respective digital representations of the object and the first and
second build style lattices. This step of overlaying the digital
representations of the lattice 54 and object is preferably
performed by use of the aforementioned Magics RP software. In order
to provide a lattice structure including interlaced build style
lattices, the overlaying step includes shifting the position of the
second build style lattice relative to the first build style
lattice to interlace the first and second build style lattices. The
shifting or offsetting of the relationship of the first and second
build style lattices will depend upon the desired configuration of
the object, but generally will be in three dimensions so that the
nodes of the second lattice build style are offset in the x, y and
z axes from the nodes of the first build style lattice.
[0063] The next step in the fabrication method is intersecting the
overlaid representations to generate a digital representation of
the object incorporating the first and second build style lattices.
The generation of a digital representation of the intersection of
the representations of the lattice 54 and object is preferably
performed through use of software available from 3D Systems, Inc.
under the name Maestro using a double or triple border compensation
with no fill.
[0064] The next step in the fabrication method is fabricating the
digital representation of the object incorporating the build style
by solid free form fabrication. This step can be accomplished
through operation of apparatus 10 or any other suitable SFF
apparatus.
[0065] In some applications it is desirable to provide different
materials for the first and second build style interfaces. In order
to fabricate such multi-material objects, the fabricating step can
include providing a first material for the first lattice and a
second material for the second lattice. The appropriate SSF
techniques for fabricating multi-material objects are additive
process of the type discussed above.
[0066] In those applications wherein the object being made includes
a boundary skin, the fabricating step includes fabricating the
boundary skin so that at least one of the first and second build
style lattices supports the skin.
[0067] In those applications wherein the object being made is to
include a lattice build style having hollow components, such as
hollow legs for conducting a fluid, the step of generating a
digital representation of the first build style includes the step
of generating a digital representation of a third build style
lattice, the overlaying step includes overlaying the digital
representations of the first and third build styles and the
intersecting step includes intersecting the digital representations
of the first and third build styles to result in the representation
of hollow legs in the first build style lattice. Also, in those
applications wherein the object being made is to include a lattice
build style having hollow components, the fabricating step includes
fabricating at least one of the plurality of legs so as to be
hollow.
[0068] Thus the three dimensional object can be formed through use
of a free form fabrication method including the steps of:
[0069] 1. generating a digital representation of the object
including a representation of a surface of the object;
[0070] 2. generating a digital representation of a first build
style lattice having a predetermined, substantially uniform
structure;
[0071] 3. generating a digital representation of a second build
style lattice having a structure similar to the first build style
lattice;
[0072] 4. intersecting the overlaid representations to generate a
digital representation of the object incorporating the first and
second build style lattices; and
[0073] 5. fabricating the digital representation of the object
incorporating the first and second build style lattices to form a
boundary skin, a first lattice integrally formed with and extending
from the skin and a second lattice interlaced with the first
lattice and integrally formed with and extending from the skin.
[0074] Various features of the invention are set forth in the
following claims.
* * * * *