US005340433A
`.
`5,340,433
`[11] Patent Number:
`p19
`United States Patent
`*
`
`Crump [45] Date of Patent:~Aug. 23, 1994
`
`
`[54] MODELING APPARATUS FOR
`TREXIMENSTONSL OBITS
`Inventor:
`S. Scott Crump, Minnetonka, Minn.
`[75]
`73]
`ee
`Paeysytny
`pe
`73] Assignee:
`Stratasys, Inc., Minneapolis, Minn.
`[*] Notice:
`The portion of the term ofthis patent
`subsequent to Jun. 9, 2009 has been
`disclaimed.
`894.248
`Jun. 8, 1992
`
`121] Appl No.
`.
`PP
`{22] Filed:
`
`No.:
`
`Related U.S. Application Data
`oo,
`ponaagoninpart ofSer. No. 429,012, Oct. 30, 1989,
`[63]
`BENG:
`Oy
`tasse7
`[SA] Tat. Cl? scsscevcseccscveveccesveccevesaccuvecvovezers B65C 11/04
`[52]
`“WSs, Ce csscsesssscvnsesavssvs.ceeeseereene 156/578; 118/202;
`156/218; 156/350; 264/25; 264/239; 425/378.1;
`425/379.1
`;
`[58] Field of Search 2.00...eceeeeeeeee 156/578, 218;
`425/378.1, 379.1, 547, 549; 264/25, 239;
`118/202, 302
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`2,708,278
`5/1955 Kamborian ..sssssssseseceeene 156/573
`2,726,629 12/1955 Paulsen ........
`.. 156/578
`
`2,762,716 9/1956 MacKenzie..
`... 156/578
`ws 156/578
`2,824,541
`2/1958 Paulsen ........
`
`6/1960 Johnson...........
`a 156/218
`2,940,888
`
`3979.190 vtee Fobason et alsees
`dene Rete
`...
`z
`p35
`attersby et
`al.
`
`3,749,149 7/1973 Paton et ab.ecco 164/50
`wae 156/578
`4,069,087
`1/1978 Liike et al.
`...
`
`1/1981 Housholder oceccsecsesseseess 264/219
`4,247,508
`4,621,762 11/1986 Bronowski ...
`wee 228/215
`4,749,347 6/1988 Valavaara ......ccsesesseees 425/135
`
`671992 (CRAMD se cecgscccssssccceesesarerseeses 264/25
`5,121,329
`FOREIGN PATENT DOCUMENTS
`0284674 10/1988 European Pat. Off.
`.
`2583333 12/1986 France .
`3904230
`8/1990 Fed. Rep. of Germany .
`.
`.
`.
`.
`Primary Examiner—David A. Simmons
`Assistant Examiner—William J. Matney, Jr.
`Attorney, Agent, or Firm—Moore & Hansen
`[57]
`ABSTRACT
`.
`.
`.
`.
`Apparatus incorporating a movable dispensing head
`provided with a supply of material whichsolidifies ata
`predetermined temperature, and a base member, which
`are movedrelative to each other along multiple axes in
`a predetermined pattern to create three-dimensional
`objects by building up material discharged from the
`dispensing head onto the base memberat a controlled
`rate. The apparatus is preferably computer driven in a
`process utilizing computer aided design (CAD) and
`computer-aided (CAM)software to generate drive sig-
`nals for controlled movement of the dispensing head
`and base memberas material is being dispensed.
`Three-dimensional objects may be produced by deposit-
`ing repeated layers of solidifying material until
`the
`
`Shape isFormed. oe malenial, such as seyhardening
`W@x€S,
`thermoplastic resins, molten metais,
`two-pa
`epoxies, foaming plastics, and glass, which adheres to
`the previous layer with an adequate bond uponsolidifi-
`cation, may be utilized. Each layer base is defined by
`the previous layer, and each layer thickness is defined
`‘
`‘
`‘
`anda. by me eightatwhich metpsf
`© Cispensing
`Aead
`1s positioned
`above
`the preceding
`layer.
`
`16 Claims, 6 Drawing Sheets
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`

`

`U.S. Patent
`
`Aug. 23, 1994
`
`Sheet 1 of 6
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`5,340,433
`
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`U.S. Patent
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`Aug. 23, 1994
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`U.S. Patent
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`Aug. 23, 1994
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`U.S. Patent
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`Aug. 23, 1994
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`Sheet 4 of 6
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`U.S. Patent
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`Aug. 23, 1994
`
`Sheet 5 of 6
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`U.S. Patent
`
`Aug. 23, 1994
`
`Sheet 6 of 6
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`5,340,433
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`7
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`

`

`1
`
`5,340,433
`
`MODELING APPARATUS FOR
`THREE-DIMENSIONAL OBJECTS .
`
`2
`Processes and apparatus also exist in the prior art for
`producing three-dimensional objects through the for-
`mation of successive, adjacent laminae which corre-
`spond to adjacentcross-sectional layers of the object to
`This application is a continuation-in-part of applica-
`be formed. However, known techniques of that type in
`the art of stereolithography require the use of a vat of
`tion Ser. No. 07/429012filed on Oct. 30, 1989, now U.S.
`liquid comprising a photo-curable polymer which
`Pat. No. 5,121,329 issued on Jun. 9, 1992.
`changes fromaliquid to a solid in the presence oflight.
`BACKGROUND OF THE INVENTION
`A beam of ultraviolet light (UV)is directed to the sur-
`face ofthe liquid by a laser beam which is moved across
`the liquid surface in a single plane, in a predetermined
`XY pattern, which may be computer generated by a
`CADsystem. In such a process the successive layers
`may only be formed in a single, horizontal plane, with
`successive layers which solidify in the liquid vat adher-
`ing together to form the desired object. Such a process
`and apparatus is disclosed in U.S. Pat. No. 4,575,330
`issued to Charles W. Hull.
`U.S. Pat. Nos. 4,752,498 and 4,801,477 issued to
`Fudim disclose more recent methods for the production
`of three-dimensional objects by irradiation of photo-
`polymers within a liquid medium. Multi-layered objects
`can be made in accordance with the teachings of those
`patents by directing photopolymersolidifying radiation
`directly into a desired area within the uncured photo-
`polymer with the use of an immersed radiation guide.
`However, here again, such processes require the use
`and handling of curable photopolymer liquids which
`are hazardous, and do not permit the forming of ultra-
`thin layers of material in building up an object with a
`very fine and smooth surface.
`U.S. Pat. No. 4,818,562 issued to Frank G. Arcella et
`al discloses a method form forming an article by direct-
`ing a laser beam to a fusible powder which is melted by
`the beam and solidifies on its surface to form an object
`of desired shape. This process is also very expensive,
`and is further complicated by the required use of a gas
`which is directed through the powder to fluidize it.
`Impurities in the gas must ultimately be removed, and
`the gas must be recirculated or vented by the use of
`complex gas-handling apparatus.
`Devices also exist for the manual making of models or
`sample articles, such as jewelry, from wax by the use of
`a wax dispensing gun from which the wax is dispensed
`in a heated, molten state. Such a wax-modeling gunis
`manufactured by the MATT Company, 663 Fifth Ave-
`nue, New York, N.Y. Also, glue guns, such as that
`manufactured by Parker Manufacturing Company of
`Northboro, Mass., are available for heating and dispens-
`ing adhesives in a fluid, molten state for gluing articles
`together. The Parker glue gun utilizes a glue stick
`which is heated within the gun and dispensed as a
`melted glue. However, neither the wax-molding gun
`nor the known glue guns have ever been adapted or
`utilized in conjunction with mechanical means through
`which the dispensing gun and/or a substrate may be
`mechanically moved with respect to each other so as to
`generate a predetermined, three-dimensional shape by
`applying successive layers of material in a predeter-
`mined pattern.
`Thus, a need continues to exist for a relatively simply
`and efficient process and apparatus by means of which
`designers may design and create three-dimensional ob-
`jects at office work stations. The process and apparatus
`disclosed herein meets that need with the same ease and
`simplicity of using a desk-top computer and printer,
`with the entire modeling process being carried out at
`the operator’s CAD workstation.
`
`This invention relates to an apparatus and process for
`forming a three-dimensional object of predetermined
`design, and in particular to the making of a model or
`article by depositing multiple layers of a material in a
`fluid state onto a base. The material is selected and its
`temperature is controlled so that it solidifies substan-
`tially instantaneously upon extrusion or dispensing onto
`a base, with the build-up of the multiple layers forming
`the desired article.
`Methods and techniques for making three-dimen-
`sional articles of a predetermined size and shape are
`known. In accordance with conventional techniques,
`the desired part is initially drawn, either manually or
`automatically utilizing a computer-aided design (CAD)
`procedure, with the article being ultimately formed by
`removing material from a block work piece to form the
`desired shape in a machine operation. The machining
`operation may also be automatic with the utilization of
`a computer-aided machining (CAM) process. This
`costly and time consuming process is repeated multiple
`times to perfect
`the final manufacturing of a part,
`model, or prototype. The designer’s success is often
`dependent upon either the interpretation or the skill of
`the machinist making the prototype or model. This
`commonpractice of mechanically removing material to
`create three-dimensional objects involves significant
`machiningskills and machining time. Chemical machin-
`ing techniques available to form objects have depth
`limitations and are incapable of making complex shapes.
`Thermal molding by injection or other molding tech-
`niques requires expensive molds and a procedure better
`adapted economically for large runs where reproduca-
`bility is required. With respect to jewelry applications,
`most custom jewelry is now produced manually.
`The current state of the art does embrace processes
`for making three-dimensional objects by building-up
`material in a pattern as prescribed by an article to be
`formed. U.S. Pat. No. 4,665,492 issued to William E.
`Masters discloses such a process wherein a stream of
`particles is ejected from a supply head and directed to
`the coordinates of the three-dimensional article in re-
`sponse to data automatically provided from a CAD
`system. This process requires a seed at the point of
`origin of the article to which the particles areinitially
`directed. The particles impinge upon and adhere to
`each otherin a controlled environmentso as to build-up
`the desired article. The Masters procedure requires the
`use of two injection heads to achieve the desired three-
`dimensional article, requires a seed at the point of origin
`about whichthe article is constructed, and thus does not
`lenditself to the formation of successive layers of mate-
`rial in a predetermined pattern as a relatively simple
`means for building-up an article, such as a model or
`prototype. The Masters system builds up the article
`from a central seed by applying material to predeter-
`mined coordinates. Such a process presents inherent
`difficulties in holding close tolerances in the 0.001 inch
`range and without accumulative error build-up.
`
`20
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`25
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`3
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`5,340,433
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`BRIEF SUMMARY OF THE INVENTION
`
`This invention has as its primary objective the provi-
`sion of a process and apparatus by means of which
`three-dimensional objects can be created at an office
`workstation in a very time and cost effective manner.It
`is anticipated that the invention will be particularly
`useful in the making of single prototypes or models of
`products so that they may be quickly made and studied
`by designers. Products having complicated shapes may
`thus be evolvedeffectively and efficiently through im-
`mediate observation of design errors and repeated mod-
`eling.
`These basic objectives are realized by dispensing a
`material at a controlled rate from a dispensing head
`unto a substrate or base member in a predetermined
`pattern dictated by the shape of an article to be formed,
`with the material being dispensed in multiple layers
`which solidify and adhere to each other to build up the
`article. The processis controlled so that the material in
`the preceding layer, and in particular at least the mate-
`rial under the dispensing head, has solidified before
`additional material is applied on top of it to form a
`subsequent layer.
`Advantageously, material is applied in a fluid state in
`very thin layers which adhereto the preceding layers in
`a multiple laminate of exceptionally smooth surface
`quality. The dispensing head is controllably elevated
`along a “Z” axis so as to sequentially form layers of
`material as thin as 0.0001 inches or as great at 0.125
`inches in thickness. The thickness of each layer is con-
`trolled by regulating the gap between the dispensing
`head and the previously-formed layer. Alternatively,
`the base member may be movably mounted for con-
`trolled up and downelevation along a “Z” axis to con-
`trol the gap between the dispensing head and the previ-
`ously formed layer. In that arrangement, the dispensing
`-head would be mounted for movementin an X, Y plane.
`In order to mechanically form each successive layer,
`drive motors are provided to selectively move the base
`member and dispensing head relative to each other in a
`predetermined pattern along “X” and “Y” axes as mate-
`tial
`is being dispensed. Relative vertical movement
`along a “Z”’ axis may also be carried out during the
`formation of each layer, as well as at the completion of
`each layer to achieve desired layer shape and thickness.
`Such mechanical movements are preferably achieved
`through drive signals input to the drive motors for the
`base member and dispensing head from a computer/-
`controller CAD/CAM system. In such a system the
`design of an article to be formedis initially created on a
`computer, with commercially available. software being
`utilized to convert the three-dimensional shape into
`multiple layer data which is transmitted as drive signals
`through a computer-aided machine (CAM) controller
`to the aforesaid drive motors. Each layer can haveits
`own distinctive shape as controlled by the program in
`the CAD system, and the layers may have different
`thicknesses.
`The article-forming material is preferably supplied to
`the dispensing head in the form ofa flexible strand of
`solid material from a supply source, such as a reel. A
`rod of solid material may also be used as the material-
`supply medium on the dispensing head. In either case,
`the material is heated aboveits solidification tempera-
`ture by a heater on the dispensing head and applied as a
`fluid. Preferably, the dispensing head includes a flow
`passage connectedto a dischargeoutlet in a nozzle from
`
`20
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`4
`which the fluid material is dispensed. The nozzle may
`advantageously function as a “doctor blade” acting on
`the surface of each layeras it is formed to closely con-
`trol the thickness of each layer.
`thermoplastic
`Various material,
`including waxes,
`resins, and metals may be used to form three-dimen-
`sional articles as described herein. The material is pref-
`erably one which will melt at a preselected temperature
`and rapidly solidify without shrink distortion upon ad-
`hering to the previous layer. A temperature controller
`responsive to temperature sensors on the dispensing
`head is used to closely control the temperature of the
`supply material to a level of about 1° C. aboveits solidi-
`fication temperature at the point of discharge. This
`ensures consistent flow and that the material will solid-
`ify substantially instantly upon cooling, after discharge,
`with resultant efficiency in the article-forming process
`as multiple layers are discharged,solidify, and build-up.
`A supplemental heater on the nozzle tip responsive to
`the temperature controller provides the close control of
`the temperature of the material as it is discharged, to
`ensurethatit is in a fluid state slightly aboveits solidifi-
`cation temperature.
`Advantageously, at least one pair of pulleys or rollers
`having a nip in between are utilized as a material ad-
`vance mechanism to grip a flexible strand of modeling
`material and advance it into a heated dispensing or
`liquefier head having an elongated material passage
`extending therethrough to a discharge orifice at the
`opposite end of the head. A thermal seal is provided on
`the material receiving end of the dispensing head to
`ensure that the continuous,flexible strand does notrise
`to a temperature such that it becomes unduly limp so as
`to fold or buckle upon being advanced by the supply
`rollers, with resulting plugging of the relatively small
`diameter, material passage extending through the lique-
`fier or dispensing head. This objective is further en-
`hancedby providing a tubular guide member having an
`elongated material passage extending therethrough in
`alignment with an aperture in the thermal seal and with
`the material passage through the dispensing head, be-
`tween the outputside of the supply rollers and the aper-
`ture through the thermal seal. The tubular guide mem-
`ber is made of highly conductive metal, such as alumi-
`num orsilver. It thus dissipates heat rapidly to maintain
`the flexible strand at a suitable temperature during its
`movement from the supply rollers into the material
`passagein the dispensing head so that the strand will not
`become limp and buckle.
`As a further beneficial aspect of the modeling ma-
`chine, one embodiment mayutilize modeling material in
`the form of a flexible strand having a hollow or tubular
`configuration. A heat conducting mandrel is supported
`in heat conductive relation to the liquefier head within
`its material flow passage, and the tubular strand is ad-
`vanced over the mandrel. Thus, the flexible strand is
`heated more thoroughly and rapidly on both its inside
`and outside surfaces.
`These and other objects and advantages of the inven-
`tion will become readily apparent as the following de-
`scription is read in conjunction with the accompanying
`drawings wherein like reference numerals have been
`used to designate like elements throughout the several
`views.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.1 is a perspective view showing one version of
`the apparatus for forming three-dimensional objects;
`
`~
`
`9
`
`

`

`6
`within its drive block 16 with a drive screw 18. A drive
`motor 20 provides rotary power to drive screw 18.
`Slide rod 14 also carries an elongated drive screw 22
`driven by a second motor 24 and coupled to mating
`threads (not shown) secured to the underside of base
`plate 10 for driving engagement therewith. It will thus
`be seen that article-receiving base plate 10 may be
`moved along the X and Y axes indicated in FIG. 1 by
`the selected actuation of motors 24 and 20, respectively.
`Separate mechanical drive means are provided for up
`and downvertical movementof dispensing head 2. For
`that purposed, head 2 is mounted for vertical movement
`on a micro-slide bearing 26 on one end of support arm
`8 by a bracket 28. One apertured end of right angle
`bracket 28 is threadedly engaged with a drive screw 30.
`A third drive motor 32 supplies driving, rotary power
`to screw 30 and is mounted on support arm 8 by bracket
`34 as shown. Selected actuation of reversible motor 32
`thus rotates screw 30 to provide up and down vertical
`movementof dispensing head 2 on slide bearing 26. For
`that purpose, motor 32 is preferably a high resolution
`stepper motor. It is to be noted, however, that various
`types of motors could be used for drive motors 20, 24,
`and 32, including stepper motors, linear motors, servo-
`motors, synchronous motors, D.C. motors, and fluid
`motors.
`
`5,340,433
`
`5
`FIG.2 is a diagrammatic view showing the comput-
`er-aided design system for operating the article-forming
`apparatus;
`FIG. 3 is a vertical section view of the dispensing
`head of FIG. 1,
`FIG.4 is a fragmentary view showing the dispensing
`head applying multiple layers of material:
`FIG. 5 is an elevation view of a different embodiment
`of the material-applying apparatus utilizing a flexible
`strand as the supply material;
`FIG.6 is a fragmentary, section view of a modified
`forth of dispensing nozzle showing multiple flow pas-
`sages;
`FIG.7 is a fragmentary, perspective view of a mani-
`fold type of material dispenser having multiple outlets;
`FIG.8 is a vertical section view of the manifold and
`valve assembly of FIG. 7;
`FIG. 9 is a diagrammatic illustration showing how
`multiple layers of material can be built up in varying
`heights and thicknesses; and
`FIG. 10 is a diagrammatic illustration showing how
`material can be dispensed and formed in free space by
`the apparatus of this invention.
`FIG.11 is a bottom plan view of an alternative multi-
`ple orifice dispensing head as viewed along lines 11—11
`of FIG.6;
`FIG.12 is a diagrammatic illustration showing how a
`wire frame article can be formed by the apparatus of
`this invention;
`FIG.13 is an elevation view, partially in section, of
`still another embodimentof the material-applying appa-
`ratus utilizing a flexible strand as the supply material;
`FIG.14 is a fragmentary, top, plan view of the heat
`dissipating fin and tubular guide memberfor the strand,
`taken along lines 14—14 of FIG. 13;
`FIG. 15 is a fragmentary, vertical section view of a
`modified embodimentof the dispensing head utilizing a
`tubular strand as the supply material in combination
`with a heating mandrel for heating the inside of the
`strand;
`FIG.16 is a horizontal section view of the apparatus
`of FIG. taken along lines 16—16 thereof; and
`FIG.17is a perspective view showing the dispensing
`head and material advance mechanism of FIG. 13
`mounted on a carriage for movementrelative to a base
`member.
`
`10
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`Preferably, for fully-automated operation, motors 20,
`24, and 32 are computer-controlled by drive signals
`generated from a computer 36, by means of which a
`computer-aided design (CAD) can be created at a de-
`sign person’s work station. Support table 12 on which
`base plate 10 is carried is of such a size that it can be
`located on a desk top. Thus, by operation of the com-
`puter keyboard 38 as shown in FIG. 1, a three-dimen-
`sional article can be designed and created at a single
`office work station by one operator,in the mannerhere-
`inafter set forth. As is indicated schematically in FIG.2,
`the design of a three-dimensional article 40 is input to
`computer 36 utilizing commercially available CAD
`software. The article design is sectioned into multiple
`layers by a commercially available software program to
`provide multiple-layer data corresponding to the partic-
`ular shape of each separate layer. Such software pro-
`grams are in commercial use for computer-aided ma-
`chining (CAM) purposes, and include NC Polaris,
`Smartcam, and Mastercam. AUTOLISP, has been suc-
`cessfully used to layer AUTOCAD drawingsinto mul-
`tiple layers or sections of specific patterns and dimen-
`sions. The layering data signals are directed to a ma-
`Referring now to the drawings, FIG.1 illustrates one
`chine controller 44 from the layering software 42 as
`embodimentof the apparatus of this invention for mak-
`shown diagrammatically in FIG. 2. Controller 44 in
`ing three-dimensional articles, the apparatus being gen-
`turn is connected to the X, Y, and Z drive motors 24, 20,
`erally indicated by reference numeral 1. The apparatus
`and 32, respectively, for selective actuation of those
`includes a movable dispensing head 2 having a dis-
`motors by the transmission of the layering drive signals.
`charge nozzle 4 at its bottom end, dispensing head 2
`Various materials in different forms may be used for
`being supported from a pedestal 6 by a mounting arm 8.
`making three-dimensional articles with the apparatus
`Dispensing head2is located in close proximity to a base
`described herein.It is preferred that the material be one
`member comprising a plate 10 on which an article to be
`which is thermally solidifiable from a fluid state in
`formed is built up as hereinafter set forth.
`whichit is applied, either at room temperature or at a
`Dispensing head 2 and base plate 10 are supported for
`predetermined temperature by the use of a cooling me-
`mechanical movementrelative to each other. In the
`dium. FIGS.1 and 3 illustrate one embodiment in which
`preferred embodiment shown,this is accomplished by
`the working material is supplied in the form of a solid
`providing mechanical means for translational move-
`rod 46, heated to its melting point in dispensing head 2
`mentof base plate 10 laterally along “X” and “Y” axes
`and dispensed from nozzle 4 as a flowable fluid.
`of a base plane andfor vertical movementof dispensing
`Various material may be used for the rod, including
`head 2 along a “Z” axis. Accordingly, as is shown in
`bees wax, casting wax, machineable and industrial
`FIGS.1 and2, base plate 10 is supported on an X-Y axis
`waxes, paraffin, a variety of thermoplastic resins, met-
`table 12 having a slide rod 14 in threaded engagement
`als, and metal ailoys. Suitable metals include silver,
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
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`7
`gold, platinum,nickel, alloys of those metals, aluminum,
`copper, gold, lead, magnesium,steel, titanium, pewter,
`manganese bronze. Glass, and particularly Corning
`glass, would also be satisfactory. Materials of varying
`degree of transparency would be useful in forming cer-
`tain objects, such as for forming windows in model
`buildings. Chemical setting materials, including two-
`part epoxies would also be suitable. Materials which
`have been found to be particularly suitable for making
`three-dimensional objects with the apparatus disclosed
`herein include Freeman “machineable wax” manufac-
`tured by Freeman Manufacturing and Supply of Cleve-
`land, Ohio, “Friendly Plastic” thermoplastic manufac-
`tured by Friendly Plastic of Boulder, Colo., bismuth
`153 alloy manufactured by Metal Specialties of Fair-
`field, Conn., and Thermoplastic Polymer No. 235-10,
`Specification No. 11061 sold by Ad-Tech of Hampton,
`N.H.
`Supply rod 46 is inserted into supply chamber 50 of
`dispensing head 2 through a guide sleeve 48 as is best
`shown in FIG. 3. Various means may be utilized for
`advancing supply rod 46 through supply chamber 50 as
`material from the rod is dispensed through nozzle 4.
`One suitable means which has proven to be suitable for
`that purpose comprises a drive rod 52 whichis attached
`as an extension to reciprocating piston 54 of a power
`cylinder 56. Cylinder 56 is a fluid cylinder which is
`preferably actuated by a supply of pressurized air
`through air line 58 from air compressor 60 andits re-
`ceiver tank 62 in which a reservoir of compressed air is
`maintained. Air from the compressor/receiver 60/62 is
`delivered through supply line 58 and a 3-way solenoid
`valve 64 and a pressure-regulating valve 66 to air cylin-
`der 56. A pressure gauge 68 is connected to the air
`pressure regulator 66, all as shown in FIG.1.
`Drive rod 52 is connected by a pivotal link 70 to a
`ratchet head 72 having one or more ratchet teeth 74
`which engage supply rod 46 to advance it downwardly
`within supply chamber 50 of dispensing head 2 towards
`dispensing nozzle 4. For that purpose, a predetermined
`air pressure, preferably at a constant level, is maintained
`on top of piston 54 within cylinder 56 so as to move
`drive rod 52 downwardly. It will be understood that as
`rod 52 is moved downwardly, ratchet teeth 74 on
`ratchet head 72 will advance supply rod 46 down-
`wardly within chamber 50. Drive rod 52 extends
`through an apertured bracket plate 78 within supply
`chamber 50, bracket plate 78 serving as a stop for a
`return spring 76 acting on the bottom ofpiston 54.
`Supply rod 46 is heated within heating head 84 to a
`predetermined temperature at which it will exceed its
`solidification temperature and melt to a flowable, fluid
`form. For that purpose, a main or primary cartridge
`type, electric resistance heater 80 is provided within
`heating head 84 within supply chamber50 of dispensing
`head 2. A suitable seal ring 83 is provided around the
`top of heating head 84. An electrical power lead 82 is
`connected to resistance heater 80 as shown in FIG.3.
`Heater 80 is closely controlled in order to heat the solid
`material of supply rod 46 to a temperature slightly
`aboveits melting point, and preferably on the order of
`1° C. above the melting point of the rod material. This
`is accomplished by the use of an electronic temperature
`controller 86 connected by an electrical lead or conduit
`90 to a first thermocouple-sensing element 88 as shown
`in FIGS. 1 and 3. Thermocouple 88 is located as shown
`in close proximity to the supply rod 46 within heating
`head 84 so as to be able to sense the temperature to
`
`8
`which the supply material is being heated. Temperature
`controller 86 has a main, adjustable controller as indi-
`cated in FIG. 1 whichis set to a predetermined temper-
`ature to which the supply rod material is heated by
`resistance heater 80, in response to sensing signals re-
`ceived from thermocouple 88.
`A heater blade 92 forming a part ofthe heating assem-
`bly is embedded in the supply-rod material as shownin
`FIG. 3 and serves to directly heat it to the predeter-
`mined temperature. At its lower end, supply chamber
`50 communicates with a flow passage indicated by ref-
`erence numeral 94 and extending through discharge
`nozzle 4 to a dispensing outlet in the form of an orifice
`98 of predetermined size at the bottom end of nozzle 4.
`A spring-loaded ball check valve 96 is located within
`flow passage 94, and opens to assist in metering the
`outlet flow of fluid material in response to the pressure
`maintained on the supply rod 46 within supply chamber
`50. Check valve 94 also eliminates leakage from nozzle
`4 whenthe system is stopped, even temporarily. Supply
`material from rod reduced to a liquid state by heater 80
`upstream of flow passage 94, flows downwardly into
`said flow passage and into dispensing outlet 98 from
`which it may be discharged onto base plate 10 to form
`layers of material in the course of building up an article.
`Thesize of dispensing outlet 98 may be varied for the
`particular application, as by using interchangeable ori-
`fice inserts in the tip of nozzle 4. Also a variable size
`orifice of the type employed in cameras for varying the
`aperture could beutilized.
`It is desired to discharge the supply material in a fluid
`state at a temperature only very slightly aboveits solidi-
`fication point, so that the material will solidify very
`rapidly upon cooling after discharge onto baseplate 10.
`To ensure that the supply material is discharged from
`outlet 98 at the desired, predetermined temperature and
`that the material is maintained in a livid state through-
`out flow passage 94, and does notsolidify therein, a
`supplemental electric heater 100 is provided on the tip
`of discharge nozzle 4 adjacentto fluid passage 94. Tem-
`perature controller 86 has a second, adjustable tempera-
`ture regulator for the tip heater 100 as indicated in FIG.
`1. That temperature regulator receives control signals
`from a second sensing device in the form of a thermo-
`couple 102 attached to nozzle 4 in close proximity to
`flow passage 94 near its outlet end. As is also indicated
`in FIG.1, the electrical connectors for thermocouples
`88 and 102 both extend through powerlead or conduit
`90 connected to the temperature regulators for the main
`heater 80 and for tip heater 100 on temperature control-
`ler 86.
`As drive rod 52 moves downwardly towards the end
`of its rod supply stroke to bring ratchet head 72 near the
`position shown in FIG.3, the piston 54 and drive rod 52
`must be retracted upwardly in order that ratchet head
`72 with its teeth 74 may take a new grip along supply
`rod 46 near its upper end. The upward and downward
`movement of drive rod 52 may be controlled by a limit
`switch within dispensing head supply chamber 50,
`which is activated by the downward movement of
`ratchet head 72 or pivotal link 70; alternatively, a timer
`106 as shown schematically in FIG. 1 may be utilized to
`time the downward movement of supply rod 46 and to
`initiate the return of drive rod 52 at the expiration of a
`predetermined time interval. Either type of control
`device would be connected to air valve 64 so as to
`de-energize that solenoid valve and cut off the supply of
`pressurized air to the top of drive cylinder 56. When
`
`5,340,433
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`60
`
`65
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`11
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`11
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`5,340,433
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`9
`that happens, return spring 76 urges piston rod 54 back
`upwardly. That movementis further assisted and per-
`mitted by the use of a quick release, vent valve 55 con-
`nected to the fitting on the top of air cylinder 56 as
`shown in FIG. 1. When the supply of pressurized air
`through line 58 to air cylinder 56 is cut off by the clos-
`ing of valve 64, the upward movement of piston 54
`under the action of return spring 76 expels the air in the
`top of cylinder 56 through valve 55. At the top of the
`return stroke of drive rod 52, ratchet head 72 takes a
`new grip on supply rod 46. Air valve 64 is then re-
`opened at a timed interval by timer 106 to again intro-
`duce a supply of pressurized air on top of drive piston
`54 within cylinder 56. The downward, supply move-
`ment of rod 46 is then reactivated. As supply rod