Note: Descriptions are shown in the official language in which they were submitted.
21 79922
~ 1
METHOD AND APPARATUS FOR PRODUCING PARTS
BY LAYERED SUBTRACTIVE MACHINE TOOL TECHNIQUES
BACKGROUND OF THE INVENTION
This application uvl~D~onds to U.S. application Serial No. 08/361,123, filed
December 21, 1994.
Field of the JnYention
The present invention relates to a method for Illallura. lulhlg tbree~ i""..l
physical structures, in response to computer output, using subtractive tool techniques in
a layered fashion. This invention additionally ~ OIl.~ ' a computer-aided apparatus
10 that sequentially sculpts a plurality of layers of two dissimilar materials to construct a
desired physical structure in a layer-by-layer manner.
Descri~tion of the Relev~llr Art
Traditionally, three~ parts have been produced using subtractive
machining methods. In such subtractive methods, material is cut away from a starting
15 block of material to produce the desired physical structure. Examples of subtractive
machine tool methods include milling, drilling, grinding, lathe cutting, flame cutting, and
electric discharge machining. While these uuuv~llLivual machine tool methods are usually
effective in producing the desired part, they are deficient in creating some complex
geometries. Such methods are usually best suited for producing Dyu.ul~LIi~,al parts and
20 parts where only the exterior is machined. However, where a desired part is unusual in
shape or has internal features, the machining becomes more difficult and often the part
must be divided into segments requiring subsequent assembly. In many cases, a particular
part cv ~ is not possible because of the limitations imposed upon the tool
placement on the part. Thus, the size and .... rv ,.li., of the cutting tool do not permit
access of the tool to produce the desired ~v ~ ulaLiull. ~ /, a great deal of
human judgement and expertise is typically required to execute ~ullv-llliondl machining
processes, making such processes relatively slow and expensive.
Various systems for three fli~--n~inn~l modeling have been proposed and/or
developed to overcome the limitations inherent in uv~,.lLiondl subtractive machining
methods. For instance, U.S. Pat. No. 3,932,923 to DiMatteo ~ --r' ' the production
of a plurality of individual planar elements, corresponding to thin cross sections of the
object to be produced, responsive to signals generated from a contour follower. The
2 1 79922
planar elements are then stacked and physically joined together by various means to form
the desired three~ n~ object. This technique has been known to be difFIcult to
apply because an u . .,. V./h~h~lill~ number of planar elements may result from high resolution
between layers, which may be required for non-uniform three-~imPn~ l objects. The
5 handling of these numerous elements, and the necessity that these elements be precisely
stacked to be within tolerances, greatly lengthens production time.
Another method of three ' ' modeling is selective laser sintering,
qJluo~.llLdli~., tcachings of which are found in U.S. Pat. No. 4,863,538 to Deckard and
in U.S. Pat. No. 4,938,816 to Beaman et al. That method, , ' the deposition of
10 a powder, such as powdercd plastic, in a bounded area to form a powdered layer. This
layer, or a selected portion thereof, is then sintered by such means as a laser to bond the
affected powder particles of that layer together, thus forming a discrete layer of the three-
.liln~ object. Successive alternating steps of powder deposition and sintering occur
until the three~:rn~nci~-n~l object is formed. Drawbacks associated with selective layer
15 sintering include the fact that only a limited range of materials can be used and the
inherent dangers presented by the production of toxic gases resulting from the reactions
with the powder, coupled with a risk of explosion.
Alternatively, powder particles may be bonded together in a layer by use of a
bonding agent, such as a ceramic. This process, known as three tlimrnc;~m~l printing and
developed at the ~ Institute of Technology by Dr. Emanuel Sachs, is similar
to selective laser sintering, except that it ~~Ulltl~UI~' using a printer irlk jet
to deposit the bonding agent in a ~ =fl area of a powder layer, rather than using
a laser to sinter the particles together.
Both powder-related techniques suffer from a drawback common to all other prior
25 art three-~" I forming techniques, with the exception of the dru-~ '
~ullv~lAiulldl machining. Namely, such processes are planar in nature, since the parts to
be collallu~ ,d are fonned of discrete layers of material. CUII~ U.,ULI.Y, a large number
of thin layers are required to form an object within given tolerances.
A three-~imrnci~n~l object may also be formed by ballistic particle ...-...r~.n..;..g,
a technique taught in U.S. Pat. No. 4,665,492 to Masters. There, a first particle,
,'( ~ ' as an origination seed and constructed of material such as steel or a ceramic,
is placed at the origin of a three--1imrn~ n~1 coordinate system. Working heads emit
2 t 79q22
~ 3
small particles or droplets of ~ for instance~ a ceramic material ~ according to ~ r~l~ a ~
CUul,'' originating from the seed. These particles bond to the seed and to each other,
whereby continued emission of droplets in the ~ d~lr~ ..,' ~l manner ultimately produces
the three~ rnpnc;~)n~l object. While a wider array of materials can be used in this
5 technique as opposed to other methods, ballistic particle .., --,.,ri- U.. ;,.~ presents inherent
tolerance problems because tolerance is a function of droplet size and droplet po~;Liollill~
accuracy, which is difficult to manage. Full},~l,llul~, the small droplet size (a droplet may
be only a few microns in diameter) results in lengthy production time.
The most widely accepted ~ 1 method of producing a three~
object is known as stereolithography, taught in U.S. Pat. No. 4,575,330 to Hull and in
U.S. Pat. No. 4,961,154 to Pomerantz et al. In this method, a bath of a photopolymer
liquid is contained in a vessel. Generally, layer-by-layer sùlidiru,aliu.. of ,ulr~l I "~i~,r :l
areas of the liquid ~hULU~UIYIII~I surface is achieved through sequential exposure to a light
source, such as a laser. Discrete layers, each newly-formed layer bonding to an
hlul~,didl~ly preceding layer, are formed until the desired three-.li.. ~;.".-~ object is
produced. As each new layer solidifies, however, a shrinkage in its volume occurs,
causing warpage, which leads to stresses in the formed part. These stresses may cause
distortions in the part and thus lead to exceeding tolerances. While Pomerantz et al.
disclose methods of ~ i,.g for the effects of shrinkage, such methods do not
20 prevent shrinkage altogether. Arlr'' "~/, stereolilho~ ,l.y is limited to use of a
photopolymer as the material from which the three-rlimpnc~ l object is ultimately
formed. Another di ~lv ,, presented by ~ rol;ll~ h,~ is that reactions with
yll~ frequently produce dangerous toxic gases.
A modified stereo~ process is taught in U.S. Pat. No. 5,û31,120 to
25 Pomerantz et al. There, a phùlupolylll~l liquid is supplied only in discrete layers, and a
supplied liquid layer, or selected portions thereof, is solidirled throughout the entire
thickness of the layer, differing from solidifying merely at the surface of a liquid bath, as
taught in the ~rulr~. .,li..". d standard s~ /' process. Any u."ulillirl.,d liquid
is removed from the layer, such as by ~ ' ~, and resultant voids in the solidirled
30 layer are filled in with a support material, such as wax. The support material is then
allowed to solidify, after which time the entire newly-solidirled layer is trimmed to a flat,
uniform thickness by such means as a machining unit. After such trimming, subsequent
2 1 79922
~ 4
layers are formed in like manner until the three--limPn~in ~1 object is produced. This
modifled process presents a greater likelihood that an object thereby produced will meet
tolerances, since no temporary support web is necessary, unlike the standard process,
where such a web must be constructed for any overhangs of the part and then removed by
5 hand. I~owever, it is still subject to the same dio~lllvduk~ associated with that standard
process Moreover, the machine required to implement the modified stereo!hhngr~rhir
process is relatively complex and costly, and the rate of object Cu~ u~liOIi is hindered by
the additional steps required in this process.
SUMMAI~Y OF THE INVENTION
It is an important object of the present invention to provide a three-~lim~nc;~m~l part
production method and apparatus which overcome the foregoing limitations associated with
prior art systems.
It is a further object of the present invention to provide a three-.l;,.,~.~;.,,.-~ part
production method and apparatus which are not dependent upon resolution of object section
15 thickness to attain a given tolerance for the object.
It is a further object of the present invention to provide a three-~ ;. ":~1 object
production method and apparatus which combines molding techniques and machining
techniques to illUI~ lly produce the three-dimrncir,n:ll object.
These as well as other objects are ~ h. d by a method of producing a three-
20 rl;.. .,- ~ object comprising the steps of depositing a first layer of mold material onto
a support surface, machining a first cavity into the frst layer of mold material,
depositing a first layer of ~u~ iull material onto Lhe first layer of mold material such
that an UV~ portion of the first layer of l_OIl~llUl.liUU material flls the frst cavity
to form a first three-rlin ~inn~l section of the object and such that a oU~ JU:~;llg portion
25 of the layer of ~:onOIIu.lion material covers the first layer of mold material, and machining
the OU,u"lluu~ g portion of the first layer of ~wlollu~liull material to form a second three-
, n~ section of the object.
When additional three-~imrn~inn:il sections are necessary to complete a three-
.li.. ,~;.n,~object,theprocessofthepresentinventionuu ~' sequentiallyrepeating
3û the following steps until the object is completely formed: (1) depositing a successive layer
of mold material onto an hl"l.r ' '~/ preceding three-dimensional section of the object,
(2) machining a ~UII~.oLlUUdil~g cavity into the successive layer of mold material, (3)
2 1 79922
depositing a successive layer of cu~ uuLiun material onto the successive layer of mold
material such that an v._~L~ul);n~ portion of the successive layer of cun,L.u~;Lic., material
flls the cù.l~,;.,uo,.di~.t5 cavity to form another three-.l;.,.~ .,.~;.,...l section of the object and
such that a ~u~u~,uu~hl~ portion of the successive layer of uull~LIu~Liol~ material covers the
5 successive layer of mold material, and (4) machining the ~U,U.lUoSi.,g portion of the
successive layer of col-,L-u~L;oll material to form yet another three-flimrnci~-n~l section of
the object.
The di'UI' ~ t;ll J objects of the present invention are also a~o...~uli~h~d by an
apparatus for producing a three-~lim~ neir-n~ll object, comprising sculpting means, a director
10 for positioning the sculpting means in a 1~ ,.,;l l area, a mold material dispenser
operatively connected to the director, a uull~Llu~Lioll material dispenser operatively
connected to the director, and a controller operatively connected to the director, the
controller controlling operation of the sculpting means to selectively sculpt mold material
and CU.~.,IU~.I;On material.
In general terms, the "layered subtractive machine tool method" ~,UIIi~,lll,U' anew and improved system for making solid objects by ~u~c,,i~,ly machining thin layers,
or laminae, of mold and wll~llu~,lioll material. The successive laminae are onn-m~ sllly
integrated as they are formed to defne the desired three-.l;~ ;.".~l object. The mold
material often provides a sculpted receptacle into which the c, u~,liu" material is
20 deposited, thereby imparting its negative shape to areas of an object which would
otherwise be difficult or impossible to machine by conventional means. Additionally, the
positive shapes of portions of the object are formed by machining layers of ~ u~lio,.
material.
In a presently preferred ~ .l,ù~' -- by way of example and not necessarily by
25 way of limitation, the present invention harnesses the principals of computer aided design
(CAD) in ~.,...l.;..-~;u.. with layered machining, i.e., the use of subtractive machining
methods on a layer-by-layer basis for forming three ~lim~nc;~mol objects, to cim~ onCly
execute CAD and computer aided ~ .uura~Lu- ..~, (CAM) in producing three-rlimrnci~
objects directly from computer instruction. Intended al,l,lic.lLic).l~ of the invention include
30 sculpting models and prototypes in a ul~lllurh~Lulhl~ system and in a design phase of
product d~clo,ul.l~.-L.
21 79q22
~ 6
The ability to sculpt three tiinlPncinn~l features into each layer makes it possible
to work with ~ olls;d.,lAbly thicker slices, thereby reducing ~ Al complexity and
CUll~llU-;liull time while increasing part tolerance. Thus, tolerances are not a function of
layer thickness but are instead largely dependent on the accuracy of the subtractive
5 machine tool methods. Additionaily, the method of the present invention provides
fiexibility in usable materials; for instance, metals, plastics, waxes, woods, polymers, and
composite materials, may be employed as UU....Iu.,liUll and/or mold materials. The term
"composite material" is intended to generally include any material made from two discrete
snhct~nf rc and more specifically is used to denote man-made cnrnroci~pc~ including fiber-
reinforced plastics. Composite materials allow a blending of properties of the separate
. " ~l,n"~ With specific reference to fiber-reinforced plastics, such composites combine
the high strength and stiffness of the fber material with the low weight and fracture
resistance of the polymeric matrix.
BRIEF DESCRliPTION OF THE DRAWINGS
The uùll~llu~.liùll designed to carry out the invention will be hereinafter described,
together with other features thereof.
The invention will be more readily understood from a reading of the following
and by reference to the - , yi-.g drawings fûrming a part thereof,
wherein an example of the invention is shûwn and wherein:
FIG. 1 is a perspective view, partly in schematic, of an apparatus ~uu~lluul~ i in
accordance with a preferred ~",ho.l;.,.. ~ of the present invention for producing three-
.i;,....,.;,.,~ objects;
FIG. 2 is a perspective view of a sphere;
FIGS. 2A-2F illustrate successive stages in the production ûf the sphere illustrated
in FIG. 2 according to the method of the present invention;
FIG. 3 is a perspective view of another three-ll;~ UAl object;
FIG. 3A is a sectional elevation view taken along line 3A-3A oi FIG. 3;
FIGS. 3B-3H illustrate successive stages in the production of the object illustrated
in FIGS. 3 & 3A according to the method of the present invention;
FIG. 4 is a ~ )~liV~ view of a three-!' ~ object varying slightly from
that shown in FIGS. 3 & 3A;
FIG. 4A is a sectional elevation view taken along line 4A-4A of FIG. 4;
2 1 79922
~ 7
FIGS. 4B-4E illustrate successive stages in the production of the object illustrated
in FIGS. 4 & 4A according to the method of the present invention, said stages being in
addition to the stages illustrated in FIGS. 3B-3H.
FIG. S is a p.,.~ view of a hollow sphere;
FIG. 5A is a sectional elevation view taken along line SA-SA of FIG. 5;
FIGS. 5B-5I illustrate successive stages in the production of the object illustrated
in FIGS. 5 & 5A according to the method of the present invention;
FIGS. 5J & 5K illustrate alternative methods of removing a void negative;
FIG. 6 is a sectional elevation view of a three-~imrn~inn~l object having a recessed
surface; and
FIGS. 6B-6E illustrate successive stages in the production of the object illustrated
in FIG. 6 according to the method of the present invention.
DESCRIPTION OF THE PR~ EMBODIMENT
Depicting the context in which the method of the present invention is executed,
FIG. 1 broadly illustrates an apparatus 10 for producing Lhree-.l; ;.~ objects which
is ~ uutl,d in accordance with the preferred l ,l.o.l;--- .d of the present invention.
Generally, apparatus 10 includes sculpting means 12 capable of moving in the directions
indicated by arrows 2 and of rotating in the direction shown by arrow 4, a molding
material dispenser 14 capable of moving in the directions indicated by arrows 6, a
uc)llaL-u.,Liull material dispenser 16 capable of moving in the directions indicated by arrows
8, and a waste remover 18. As will be shown with regard to FIGS. 3E & 3G, dispensers
14 & 16 are preferably operable to dispense a plurality of mold materials and u~ LIul liu
materials, ~ ti~",ly.
Mold material dispenser 14 is shown dispensing mold material 22' from its outlet14a. The mold material, as well as c uuLion material, may ~ ,ly be deposited
by other means, such as particle beam or particle spray, pouring or spraying of liquids,
or deposition of powders for fusing after deposition. The mold material 22' is deposited
onto a support surface or platform 20 until an initial layer of mold material 22 is formed.
An example of a mold material is a water soluble wax, such as that sold by YatesInvestment Casing Wax of Chicago, Illinois under the name 550-GOLD SLAB, B4041.
Further examples will be discussed in detail later herein.
2 i 79~22
~ 8
A first director 24 is operatively coupled to the sculpting means 12 for pu~;Lùn;ll~;
the sculpting means in a ~ ".,;,.. d area, such as area 26 on the top surface 28 of the
initial mold material layer 22. Of course, the area 26 may be three-rlimr~ncinn~ thus
forming a cavity within the mold material layer 22.
Like the sculpting means 12, the molding material dispenser 14 and the
~,UII;~Il Ul,LiUn material dispenser 16 may also be operatively coupled to the first director 24.
~onn~ctinne between dispensers 14, 16 and the first director 24 are shown at 15 and 17.
Alternatively, dispensers 14, 16 may be u~lùbDIIu-LiY~ly attached to the milling head of
sculpting means 12 to constantly move with means 12. Still further, dispensers 14, 16
could be positioned by a separate director, such as second director 25 which, in turn,
could be operatively connected to a second controller such that deposition of materials and
machining of previously-deposited material layers could occur silllullall.uu~ly.A second director 25, operatively coupled to waste remover 18, may also be
provided for directing waste remover 18 in a p,~rl. t.. ,..;". d path, such as 27, for removing
15 waste material in a manner to be discussed in detail herein.
A controller 30, s~h~ irally shown as being operatively coupled to the director
24, controls operation of sculpting means 12 to selectively sculpt deposited layers of both
mold material and ~UI~Llu Liul. material.
Sculpting means 12 preferably comprises a three-axis computer Ill~ ally
20 controlled ("CNC") milling machine with tool changing ability, Illallulid~Lu.~d by
Bridgeport Machines, Inc. of Bridgeport, (~nnnrrtirllt as Model No. 760/22 DX.
Sculpting means 12 preferably includes a fixture (not shown) for holding a plurality of
iut~.~,llà.lgcdblc cutting tools, such as at 32, a cutting tool changer apparatus (not shown),
and a cutting motor (not shown) for turning tool 32. To provide quick and efficient
25 production of an object within tolerances, the cutting tool 32
may be: lly changed during operation such that a tool si~ and shape a~lJl UIJI ' '
to the geometry being ~ull~LIu~Ltd may be used. ~or example, a small spherical tool may
be a~/lupl for small curved details, a small cylindrical tool may be a~ lu~n forsmall vertical walled details, and a larger tool of an a~ u~l geometry may be used for
30 roughing in of the shape or for areas requiring lesser detail. This ability allows production
of parts with area specific tolerances.
21 79922
g
First director 24 preferably comprises a system of stepper motors, worm gears, and
linear sliders (not shown) for positioning the sculpting means 12 in three rlim~~ 7nc The
type and power of sculpting means 12, the stepper motors, and the cutting motor is
dependent upon many factors, and in particular upon the type of materials being dispensed
5 and the desired tolerance of the part being produced. Second director 25 lilcewise
comprises a system of stepper motors, worm gears, and linear sliders to move waste
mover 18 in a ,UIC~ d path.
The controller 30 preferably comprises a computer which is operatively connectednot only to first director 24, as previously described, but also to second director 25 for
controlling waste remover 18. Additionally, by virtue of the ~ : 15 and 17 to the
first director 24, controller 30 controls deposition of both mold material and uul~lu~Liu-
material. The computer comprising controller 30 preferably illUOl,Ul ' a Illi.lU~,lUCc.,~ul
34 for controlling all of the ~rul~ ' functions and a CAD/CAM system 36 for
generating ~lim~nri~n~l data for tlle object to be produced. Cuul~)u.~./cullLIuller 30 is
15 preferably capable of monitoring a position of sculpting means 12 during its removal of
extraneous material and is ~IU~, ' with i..rc,.ll..lLiul. indicative of ~ d~tcllllhl~d
boundaries of a plurality of three-.l; - .---l sections of the object to be produced.
The production of various examples of three-rlimpncii7n:~l objects will now be
described, with reference to the remaining figures.
FIG. 2 illustrates a frst example part, a sphere 38, the ~oll~Llu-Liull of whichinvolves the least amount of steps in a method of the present invention. Sphere 38 is
comprised of frst and second three-~ sections 38a and 38b, I~ Livc:ly, these
sections being .1; ~d.."..;~l ~d by imaginary equator 39, integrally joined to one another, and
formed as described below.
In FIG. 2A, a first layer of mold material 40, ~UII~ JUIIdill~; to layer 22 in FIG.
1, has been deposited onto platform 20 by mold material dispenser 14. The layer 40 is
deposiLed on platform 2û either in a solid form or as a liquid which is caused to solidify
upon or shortly after deposition. The solill;r~ of this layer may be caused by, but
not limited to, thermal, radiation, or chemical methods. A smooth upper surface 41 may
be obtained by machining if desired. Vertical walls 21 may be provided on either side of
layer 40 to act as a mold material container in c.~n; -- ii.." with platform 20. These walls
may be sections of a cylindrical wall or may be walls of a rectangular enclosure. Such
'10 ' 2 1 79922
an ~ .",~ lll is particularly desirable where the viscosity of the mold material or
uv~tluulion material in its liquid phase is relatively low, or where curing times are
relatively long.
.Sl~hseq~Pn~ to the deposition and ~ulidirl~,liù,l of layer 40, subtractive machine tool
5 methods are used to three-fiimpnc;~ iiy sculpt the mold material into a geometry specifed
by the computer control system. FIG. 2B illustrates layer 40 as having been machined or
sculpted such that a cavity 42 has been formed therein. The depth "d" of cavity 42 is
equal to the radius of sphere 38. Waste particles 44 resulting from the machining of
cavity 42 are shown to be Iying in the bottom portion thereof.
In the remaining figures to be described, although platform 20 and vertical walls
21 will not be therein shown, it is understood that any initial layer of mold material will
be considered to have been deposited upon platform 20 and within vertical walls 21 where
desirable.
FIG. 2C illustrates removal of waste particles 44 from machined cavity 42 by waste
remover 18. Preferably, waste remover 18 comprises a vacuum head 46 connected to a
suitable conduit 48 for conducting the particles 44 in the direction shown by arrow 50.
Second director 25 (FIG. I) is constructed so as to direct remover 18 not only to the area
of cavity 42 but also to any upper surface of layer 40, such as surface 41. Alternatively,
waste removal may be facilitated by use of a directed air stream which would serve to
push any debris off the layer 40. As a further alternative means of removing waste
particles, surfaces of layer 40 may be swept by an automated brush. Additionally, if
particles 44 are comprised of a metallic material, waste removal may be facilitated by
magnetic or cle~llu~ldti~ attraction. Any CVInIJ "nn of the above methods may beemployed to ~rf n~rlich waste removal.
PIG. ZD shows a layer of .on~l~u.liun material 52 as having been deposited upon
mold material layer 40. An uv~ g portion 52a of layer 52 is shown as having filled
cavity 42, thereby forming first three- ' ' section 38a of sphere 38 (FIG. 2). As
used herein, the term "overlap" and variations thereof, as ~ ,. J from the prior art
"discrete level" l~llllhlulv~y~ mean that the deposition or machining of mold or~v~ l u~liu~ materials may occur below elevations of upper surfaces of previously
deposited layers. For specific example, following deposition of layer 40, subsequent
process steps were not directed merely to areas at or above elevation "e" of surface 41 of
11 2 1 79922
layer 40: machining of cavity 42 to depth "d" (FIG. 2B) occurred below elevation "e", and
a portion of the ' ~ 'S,-added .v~ u~,liuil material layer 52 flowed below elevation
"e", into cavity 42.
Additionally shown in FIG. 2D, a DU~ JOD;llg portion 52b of layer 52 is shown
5 to cover layer 40. As used herein, the term "cover" and variations thereof mean that one
DUIJl..l~)OD;llg layer need only interface with a segment of the upper surface of another layer.
For specific example, although FIG. 2D shows the width w' of layer 52 extending the full
width w of layer 40 for simplicity of i" , thus showing an interface between layer
52 and the full length of surface 41, such a width magnitude is not always necessary.
10 Depending on the dimension of the next three-riimpnci~\n:ll section to be produced, width
w' may be less than width w. All that is required for layer 52 to "cover" layer 40 is that
there be an interface between layer 52 and a portion of upper surface 41 of layer 40.
An imaginary line 51 is shown in FIG. 2D for purposes of illustration to divide the
~ul~llu~Liull material layer 52 into the portions 52a, 52b. The c,ull~Lluuliull material layer
15 52 may comprise a ".~ le wax, such as that sold by Yates Investment Casing Wax
of Chicago, Illinois under product number B-3096. It is ~Oll'C ~ ' ' however, that other
uul~ uDiliùns may be used as ~vllDllu liull material, so long as such c.. ~po~;li....~ possess
suitable physical strength, stiffness, flexibility, and resistance to thermal .irE",.,I I j~n
FIG. 2E depicts the machining of DUI/..I,UU~ S portion 52b of l,UllDllUUIiUll material
layer 52 by sculpting means 12, thereby forming the second three-~lim~ ncin~ ~ section 38b
of sphere 38. Upon completion of this machining step and after any necessary removal
of waste particles in the manner described with regard to FIG. 2C, the completed sphere
38, partially encased in the mold material layer 40, emerges, as shown in FIG. 2F.
Mold material removal is performed following completion of the last three-
25 ~ ;n,.l section of an object. The molding material 40 may be removed, or separated
from sphere 38, physical means, radiation (electrical, UV, thermal, ultraviolet, etc.),
ultrasonic, vibration, electrical induction, or other means or methods such that the
~ollallu.liu.l material is not comprised. FIG. 2F illustrates an early stage of mold material
removal, wherein a heating device 54 begins to reduce layer 40 to a liquid mass 40a.
Complete removal of layer 40 results in an isolated completed sphere 38 (FIG. 2).
Although removal of the mold material layer 40 is shown for purposes of illustration in
FIG. 2F as being ~ ", ~ h ~l by the heating device 54, it must be kept in mind that such
2 ~ 79922
~ 12
means would not be used where the layer 40 is a water soluble wax and where the
~VII~UU~liUII material layer 52 is a ~ ,le wax, since these materials possess similar
melting points. Instead, removal of such mold material would be d.uull,~ l merely by
dissolving the mold material in water.
It is understood that all machining steps ' 7l 1Pntly mentioned herein will be
considered as having been performed in like manner to the machining steps described with
regard to FIGS. 2B ~ 2E. It is additionally understood that any s l~c-, 'y
described step of mold material removal will encompass the means discussed with regard
to FIG. 2F. Moreover, although waste particle removal will not be discussed with regard
to the remaining figures, it is understood that waste removal according to the means
discussed with regard to FIG. 2C may occur subsequent to machining of any layer of mold
or cu~ u.Livl, material and before the deposition of a subsequent mold or ~vu~LIu~,lio
material layer.
The method of the present invention may be employed to produce three-~l;, . ,. . , -l
objects possessing a more complex shape than that of the sphere 38 of FIG. 2. For
instance, FlG. 3 illustrates a rounded barbell-shaped three~ object 56 comprisedof a neck portion 58 i~,.,: -'i,.~ in end members 60, 62 at either end thereof.
As seen in FIG. 3A, object 56 may be subdivided into several lnt~ t~. ' three-
~irnPncion:ll sections 56a, 56b, 56c, and 56d. The thickness and placement of these
sections are parameters which are Inu~ Idullllcl into CAD/CAM system 36 of computer
30 (FIG. 1), and these parameters may vary according to the desired object ~.l, -- .., t~ 1 i. C
such as materials, tolerances, and speed of uull~LIu~liuu. As seen in FIG. 3A, the
n(~mrn~;tinn of sections 56c, 56d differs from that of sections 56a, 56b. It is also seen that
if object 56 were to be wholly produced by ~u.lv~..llivndl machining lerhnirlllPs, an
25 operator would have difficulty in properly positioning a tool below the u.~,lL~n~illg shape
formed by end member 62. Thus, only section 56d could be produced in such a manner
without ~ U ' illlj; significant dimculty.
In FIG. 3B, a first layer of mold material 64 has been deposited onto a support
surface in the same manner described with regard to FIG. 2A. Additionally, a first cavity
30 66 is shown as having been machined into layer 64.
In FIG. 3C, a frst layer of cuu~llul,lion material 68 is shown as having been
deposited onto the first layer of mold material 64. An uv~,.la~ illg portion 68a of layer
2 1 79922
~ 13
68 is shown as having filled the first cavity 66, thereby forming first three~
section 56a of object 56 (FIG. 3A). Additionally, a :~U~ V~hlg portion 68b of layer 68
is shown to cover mold material layer 64. An imaginary line 61 is shown for purposes
of illustration to divide the first ~o.~ u~liun material layer 68 into the portions 68a, 68b.
FIG. 3D depicts sculpting means 12 machining ;.. l~.,uosh-g portion 68b of the first
~:UII~IlU~iUn material layer 68, thereby forming the second three-~l;..,..,~;...,..l section 56b
of object 56. The outline of the portion of section 56b yet to be formed in FIG. 3D is
shown in phantom lines. The height of section 56b illustrates that an object produced by
the prvcess of the present invention need not be formed in a plurality of equally-thin planar
10 sections, as required by prior art processes, thus greatly increasing the speed of
production. To provide a smooth surface to facilitate further cu,.~L.uuliu.., upper end 69
of section 56b may be further machined using any tool which levels the surface of end 69.
Referring to FIG. 3E, a second layer of mold material 70 has been deposited on
the first layer of mold material 64 such that the second layer of mold material 74
15 completely covers the second three-~' ' section 56b. As seen from the cross
hatching in the region l~ uLi--g second mold material layer 70, that layer is shown to
be of a cu.l-l)u~ilion differing from that of the first mold material layer 64. Differing
f.,,.,l.h~;lio--- between mold material layers may not always be necessary; however,
conditions may require differing ~ ;v~ in some instances, and the process and
20 apparatus of the present invention provides the flexibility to ~ r~m~ h deposition of
differing u o---~v~;Lions. For instance, the cunll)va;Lion of the first mold material layer 64
may be that of a water soluble wax, while that of second mold material layer 70 may be
a ceramic. To provide a further example, first mold material layer 64 may be onerV .. I~ .n of a ceramic, while the second mold material layer 70 may be another25 rv~u,uldlio" of a ceramic. Any differing romrf~ nn may be used for a mold material
layer, so long as that "~ t~ n possesses the desirable properties discussed previously
and so long as that nnmr~ is compatible with the uu~ lu~,lioll material which will
interface with it. The term "compatible", as used herein to dcscribe I~J.lLivl~ ) between
mold and cul~Llu-Lioll materials, generally means that removal of mold material interfacing
30 with a given section of CUII~LIu~,Liull material will not damage or impair that ~ullaLIu~.Liu
material section.
2 1 79922
FIG. 3F illustrates a second cavity 72 as having been machined into the second
mold material layer 70.
In FIG. 3G, a second layer of COI~Ilucliu~ material 74 has been deposited onto the
secûnd layer of mold material 70 such that an UV.,I; rr lg portion 74b of second5 UUII~llUCliUII material layer 74 fills second cavity 72 to form the third three~
section 56c of object 56 (FIG. 3A) and such that a ~U~ /ODillg portion 74b of layer 74
covers the second layer of mold material 70. An imaginary line 71 is shown for purposes
of illustration to divide the second ~ U iiUl- material layer 74 into the portions 74a,
74b. As shown by the shading in the area lC~Jl..,.,lltillg the second layer of UOII~lUC~iUII
10 material 74, that layer is of a ~ " differing from that of the first layer of
cu ~ ;n.. material 68 (FIG. 3C), from which the first and second three-.li..,~"~sections 56a, 56b have been formed. For example, the frst layer of coll~llucliull material
68 may be a ~ IC wax, as previously indicated, while the second layer of
cul~llucliull material 74 may be an epoxy or a photopolymer. Cuu~u~uLly, the finished
15 object 56 may be comprised of non-l~, 'L '"' - material. Various culllLJu~;liù.~ may be
used for a cul~llu.,Liul~ materials, so long as such ~...l.n~ are sufficiently, ' ' l
when in solid form and so long as they are compatible with the . ' ~ mold material.
FIG. 3H depicts sculpting means 12 machining ~UIJ~,l,U(J:~illg portion 74b of the
second~u..~llucliullmateriallayer74~therebyformingthefourththree-1l;~" ~ section2û 56d of object 56. The outline of the portion of section 56d yet to be formed in FIG. 3H
is shown in phantom lines. Further machining may be performed, if necessary, to level
the top surface 75 of section 56d. Following the step shown in FIG. 3H or any such final
machining, the mold material layers 64, 70 may be removed by any of the techniques
discussed with regard to FIG. 2F which are suitable for the particular mold material
25 ru~ J~;li,.~ used. The removal of the mold material layers exposes the completed object
56 (FIG. 3).
The steps described with regard to FIGS. 3B-3H may be sequentially repeated to
produce additional three-~ llAl sections until a larger object is completely formed.
For instance, FIGS. 4 & 4A illustrate another three-~l~rAPn~innAl object 76 which is
comprised of object 56 (FIG. 3) and a raised inverted conical member 78 disposed upon
upper surface 75. Member 78 is subdivided into two three-.l.. ~;n., l sections which,
since object 56 was shown to have four sections, are fifth and sixth threc-~lirA.- ncinnAAI
21 79922
sections of object 76, namely ffth three~ i"".l section 76e and sixth three-
.l;, .... ,~;....~1 section 76f. As with object 56, the thickness and placement of these sections
are parameters which are programmed into CAD/CAM system 36 of computer 30 (FIG.
1), the parameters being variable as previously described.
In FIG. 4B, a successive layer of mold material is shown to have been deposited
onto an i ' 1y preceding three- li.~ iùnal section. Specifically, a third layer of
mold material 80 is deposited onto the second layer of mold material 70, and layer 80 is
seen to completely cover the i.. ~,Ji2ll~1y preceding completed three- li~ ;vllal section
76d (cullc~vllJi-lg to section 56d in FIG. 3A).
FIG. 4C illustrates a Lullc~JullJhlg cavity 82 as having been machined into the
vhird layer of mold material 80.
In FIG. 4D, a successive layer of cull~llu~liùn material is shown to have been
deposited onto the successive layer of mold material. Specifcally, a third layer of
CWI~llucliull material 84 has been deposited onto third layer of mold material 8û such that
an uv~ ri hlg portion 84a of layer 84 flls the CUllC~tJol-Uillg cavity 82 to form ffth three-
,' l section 76d and such îhat a, ~/..tJV~hlg portion 84b of layer 84 covers the
third layer of mold material 80.
FIG. 4E depicts sculpting means 12 machining :~U~ lU~illg portion 84b of the third
cv~ u~liu-- material layer 84, thereby forming the sixth three-~ Pne~ section 76f.
20 The outline of the portion of section 76f yet to be formed in FIG. 4E is shown by a
phantom line. Following any necessary final surfacing and removal of mold material
layers 64, 70, and 80, the completed object 76 (FIGS. 4 & 4A) emerges.
The process of the present invention may also be used to produce hollow three-
objects, the term "hollow" including any finished three-~ qnci~mAl object
25 which possesses at least one void at any point within its volume.
FIGS. 5 & 5A illustrate a hollow sphere 86 comprised of first and second three-
AI hollow sections 86a and 86b, respectively, which are ù~,..-~u ' by an
imaginary line 91. The internal walls of sections 86a, 86b form an enclosure 88 to defne
a void 90.
In FIGS. 5B & 5C, one layer of mold material 92 has been deposited, and a first
cavity 94 has been formed into layer 92.
2 1 79922
~ 16
Moreover, excess mold material is machined away so that mold material layer 92 has level
upper surfaces such as at 95.
FIG. SD illustrates one layer of ~.UII:~IlU~,liUll material 96 having been deposited
onto mold material layer 92 such that layer 96 fills the first cavity 94.
In FIG. 5E, e uuliull material from layer 96 which was above the elevation of
surface 95 has been removed. F~..lh..l~llul~;, a second cavity 98 has been machined into
the remaining U~,liUII material layer 96 to form first hollow three-~' ' section
86a of hollow sphere 86.
FIG. 5F illustratcs another layer of mold material 100 having been deposited onto
the one mold material layer 92 such that an u .. ,1': p~ ~ ,, portion lOOa of layer 100 fills the
second cavity 98 to form a first portion 102a of a void negative and such that au~ 6 portion lOOb of layer 100 covers layer 92 and the first three~
hollow section 86a. Imaginary line 91 divides the mold material layer 100 into the
portions lOOa, lOOb.
FIG. SG depicts sculpting means 12 machining . . ~ portion lOOb of the
mold material layer 100, thereby forming a second portion 102b the void negative 102.
The outline of the portion of void negative 102 yet to be formed in FIG. 4E is shown by
a phantom line.
In FIG. 5H, another layer of cul~lluuliull material 104 has been deposited onto the
one layer of mold material 92 such that the layer of u~,liull material 104 completely
covers the second portion 102b of void negative 102.
Referring to FIG. 51, layer of UOll~llU~liUn material 104 is shown being machined
by sculpting means 12 to form the second three-~ hollow section 86b of hollow
sphere 86. The outline of the portion of section 86b yet to be formed in FIG. 5I is shown
by a phantom line. It is seen that hollow sections 86a, 86b form the enclosure 88
P... ~ a ~ g the void negative 102.
FIGS. 5J & SK disclose alternative methods of removing void negative 102 from
enclosure 88 so as to produce the void 90 (FIG. 5A).
In FIG. SJ, a vent 106 is shown as having been inserted through second three-
~ hollow section 86b. A conduit 108 ~" with the outlet of vent 106
at one end and with a vacuum source 110 at another end. Activation of source 110 causes
the void negative material 102', which must be in a liquid or gaseous state, to escape from
2 1 79922
17
enclosure 88 in the direction indicated by arrow 112. If necessary, the void negative 102
may be partially dissolved prior to evacuation. Such dissolution may be effected by a
solvent which, depending upon the . ~ n of Ihe void negative 102, may be such
liquids as water or kerosene.
In FIG. 5R, which illustrates a therrnal method of void negative removal, a
different void negative material 102" is shown, since for such a method the material 102"
must have a lower melting point than the material comprising mold material layer 92.
Moreover, FIG. 5K illustrates the second three-dimpn~inn~l hollow section 86b as having
been formed of a porous material, such as a porous ceramic, as shown by a plurality of
pores 114, the relative diameters of which are ~ ,r ~t d for purposes of illustration.
The hollow sphere sections 86a & 86b, mold material layer 92, and the material 102" are
subjected to a heated ~llvilu~ lL such as that defined by enclosure 116. Heatingcontinues, causing material 102" to boil and reach a vapor state, whereafter the vapor
escapes through the plurality of pores 114 and into the c~uvilvll~ L 117 in the manner
indicated by arrows 118.
Void negative 102 may also be removed by a modified process including steps
illustrated with respect to both FIG. 5J & 5K. Specifically, a heated ~llvilulllllCllL may
liquify the void negative 102, whereafter the material is evacuated via a vent though a
three-/l; n.. ~i.. ~l section.
For purposes other than that shown in FIG. 5K, .llvhulllll.llL 117 need not be
limited to a heated .llvhulllnc.lL. For illustrative examples, it may be advd..t~ ,uus to cool
that .llvhulllll~,llL so as to cause rapid sùlilliri.dLiull of waxes or to flood the .llvhu~ ..lL
with an inert gas to prevent unwanted byproducts from process steps performed upon mold
or u~,Liun material.
The process of the present invention may also be used to produce a three-
d;"....~, ' object having a recessed surface, such as the object depicted in cross section
in FIG. 6, where a three--lim~nsin ~l object 120 is shown having a recessed surface 122.
Surface 122 forms an arcuate indentation with respect to the plane containing either or
both of lower planar surfaces 121 and 123. The sequential steps executed to produce
30 object 120 are described below.
FIG. 6A illustrates a layer of mold material 124 as having been deposited.
FIG. 6B depicts sculpting means 12 machining the mold material layer 124 to form
21 79922
18
a iuLulub~dll~c 126 which, though shown as having a rounded or h~,...;~,)ll..;udl shape, can
assume any shape, depending on the shape of the ~Ull~aLJU~ g recessed surface in the
object to be produced. In FIG. 6B, iuluLulJ~Idll ~ 126 thrusts outwardly with respect to
L~ uu.,diillg upper planar surfaces 124a, 124a' formed by the machining of layer 124. The
S outline of the portion of iuluLubcldllLc 126 yet to be formed in FIG. 6B is shown by
phantom lines.
In FIG. 6C, a layer of ~,uuaLluuLiOll material 128 is shown as having been deposited
onto the layer of mold material 126 such that layer 128 is seen to completely cover
i''l' dll.C 126.
As seen in FIG. 6D, machining of the uollal~uL liuu material layer 128 by sculpting
means 12 then occurs such that object 120 begins to emerge, the ~ pl~t~d portion of
which is lLi~lL,.~ilt~.d by phantom line 129.
FIG. 6E depicts the removal of machined mold material layer 124. Mold material
layer 124 is submerged into a solvent 130, which is contained in vessel walls 132 and
15 which may be water if the mold material is a water-soluble wax. As seen in FIG. 6E,
former layer 124 is shown as having been partially dissolved into a material mass 124'.
Continued s ' -~ ~-- results in complete removal of tbe mold material. It is to be again
understood that mold material removal may take place by any of the techniques discussed
with regard to FIG. 2F which are suitable for the particular mold material uulllpuailiulia
20 used.
Due to the shape of object 120, in which no overhangs are present, only one
arplir~ition and machining of a r UL liun material layer need occur, such that the only
three-(l;'- .I~;I~IIAI section produced is the entire object 12û itself. It will be aiu"l~ l,
however, that objects of different cwirli,u,dliulia, such as those with both overhangs and
25 a recessed surface, can be produced by a L.lll hjl lj,"~ of the steps described with respect
to FIGS. 6A-6E and preceding figures such that a plurality of three-11;.. ~ sections
may have to be formed.
As the foregoing description is merely exemplary in nature, being merely
illustrative of the invention, many variations will become apparent to those of skill in the
3û art It is to be iuAliiuulL.ly understood that the process steps l~a~ Li~l.y described in
FIGS. 2A-2F, 3B-3H, 4B-4E, SB-SK, and 6A-6E may be combined in any sequence to
produce three-~' l objects possessing widely varying external and internal
2 1 79922
* 19
c~ r~ a~ Such variations are included within the spirit and scope of this invention
as defined by the ~ollowing appended claims.
