Int. CL
`(51)
`(75) DO4H=1/16Inventors: Benjamin N. Dunn, Savage, MN (US); (2006.01)
`
`
`James W. Comb, Hamel, MN (US):
`(52) WES. Cla csssecoscereeenenceny 264/40.4; 264/113
`Hans P. Erickson, Eagan, MN (US);
`Jason P. Wanzek, Bloomington, MN
`(67)
`ABSTRACT
`(US)
`The present invention is a method for performing a calibra-
`tion routine of a deposition device in a three-dimensional
`modeling machine that deposits a material
`to build up
`three-dimensional objects as directed by a controller on a
`substrate mounted on a platform. The method comprises
`generating a material build profile, which represents a three-
`dimensional structure at defined locations. A relative posi-
`tion of the material build profile is then determined. An
`expected build profile is identified and then comparedto the
`determined relative position of the material build profile to
`identify any difference which represents an offset. The
`modeling systemthen positions the deposition device based
`
`(21) Appl. No.:
`
`11/397,012
`
`as) United States
`a2) Patent Application Publication co) Pub. No.: US 2007/0228592 A1
`
` Dunnet al. (43) Pub. Date: Oct. 4, 2007
`
`
`US 20070228592A1
`
`(54) AUTO TIP CALIBRATION IN AN
`EXTRUSION APPARATUS
`
`Publication Classification
`
`
`
`Correspondence Address:
`KINNEY & LANGE,P.A.
`THE KINNEY & LANGE BUILDING
`312 SOUTH THIRD STREET
`MINNEAPOLIS, MN 55415-1002 (US)
`
`
`(73) Assignee: Stratasys, Inc., Eden Prairie, MN
`
`uponthe offset.
`
`(22)
`
`Filed:
`
`Apr. 3, 2006
`
`1
`
`Shenzhen Tuozhu 1007
`
`1
`
`Shenzhen Tuozhu 1007
`
`

`

`Patent Application Publication Oct.4,2007 Sheet 1 of 15
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`US 2007/0228592 Al
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`ANOl
`
`MEMORY
`
`CONTROLLER
`
`28a
`
`X-Y¥ AXIS
`RANSLATOR
`
`32
`
`34
`
`\“wn
`
`28c
`
`MATERTAL
`SUPPLY
`
`30
`
`Z AXIS
`RANSLATOR
`
`-7iMx-=),HNaS28b
`
`2
`
`
`
`

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`Patent Application Publication Oct.4,2007 Sheet 2 of 15
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`US 2007/0228592 Al
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`100
`
`\.
`
`GENERATEMATERIAL BUILD
`
`PROFILE WITH DEPOSITION DEVICE
`
`DETERMINE RELATIVE POSITION
`OF MATERIAL BUILD PROFILE
`
`IDENTIFY EXPECTED
`BUILD PROFILE
`
`COMPARE MATERIAL BUILD PROFILE
`AND EXPECTED BUILD PROFILE TO
`IDENTIFY OFFSET
`
`POSITION DEPOSITION DEVICE
`ACCOUNTING FOR OFFSET
`
`FIG. 2
`
`102
`
`—©7.4
`
`106
`
`108
`
`— aCS
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`3
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`

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`US 2007/0228592 Al
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`Patent Application Publication Oct. 4,2007 Sheet 3 of 15
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`4
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`

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`lication Publication Oct. 4,2007 Sheet 4 of 15 US 2007/0228592 Al
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`FIG.4
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`5
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`

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`Patent Application Publication Oct.4,2007 Sheet 5 of 15
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`6
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`Patent Application Publication Oct. 4,2007 Sheet 6 of 15
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`BS 20
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`Ww
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`FIG.6B
`[I-38°40
`
`36
`
`Y
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`54
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`< 0 O4i
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`—_—_-—_-—
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`7
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`Patent Application Publication Oct. 4,2007 Sheet 7 of 15
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`FIG.7B
`FIG.7A
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`8
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`Patent Application Publication Oct. 4,2007 Sheet 8 of 15
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`FIG. 8A
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`9
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`Patent Application Publication Oct. 4,2007 Sheet 9 of 15
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`FIG. 8B
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`10
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`10
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`220
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`NINN
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`234
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`Patent Application Publication Oct.4,2007 Sheet 10 of 15
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`(aN
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`_ FIG.9
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`11
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`Patent Application Publication Oct.4,2007 Sheet 11 of 15
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`220
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`12
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`12
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`FIG. 11
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`13
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`13
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`Patent Application Publication Oct.4,2007 Sheet 13 of 15
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`200
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`\
`
`POSITIONSENSORINPROXIMITY
`
`OF A PRESELECTED TARGET LOCATION
`
`DRIVE PLUNGER INTO A
`SURFACE OF THE TARGET
`
`MONITOR CHANGE IN SENSOR
`OUTPUT SIGNAL
`
`ELECTRICALLY RECORD POSITION
`CORRESPONDING TO
`SIGNAL CHANGE
`
`202
`
`204
`
`206
`
`208
`
`REPEAT STEPS 202-208 AT ADDITIONAL|210
`PRE-SELECTED TARGET LOCATIONS
`
`SWITCH PLUNGER BACK TO
`STORED POSITION
`
`212
`
`FIG. 12
`
`14
`
`

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`Patent Application Publication Oct.4,2007 Sheet 14 of 15
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`©—
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`
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`FIG.13A
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`15
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`15
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`FIG.13B
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`16
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`16
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`US 2007/0228592 Al
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`AUTO TIP CALIBRATION IN AN EXTRUSION
`APPARATUS
`
`
`
`CROSS-REFERENCE TO RELATED
`
`
`APPLICATION(S)
`
`[0001] None.
`
`BACKGROUNDOF THE INVENTION
`
`[0002] The present invention relates to the fabrication of
`three-dimensional objects using additive process modeling
`techniques. More particularly,
`the invention relates to a
`methodfor calibrating extrusiontips in a three-dimensional
`modeling machine.
`
`[0003] Additive process modeling machines make three-
`dimensional models by building up a modeling medium,
`usually in planar layers, based upon design data provided
`from a computeraided design (CAD) system. A mathemati-
`cal description of a physical part to be created is usually split
`into planar layers, and those layers are individually shaped
`and applied to produce the final part. Three-dimensional
`models are used for functions including aesthetic judgments,
`proofing the mathematical CAD model, forming hard tool-
`ing, studying interference and spaceallocation, and testing
`functionality. The dominantapplication of layered manufac-
`turing in recent years has been for rapid prototyping.
`
`[0004] Examples of apparatus and methods for making
`three-dimensional models by depositing solidifiable model-
`ing material are described in CrumpU.S. Pat. No. 5,121,329,
`Batchelder, et al. U.S. Pat. No. 5,303,141, Crump USS. Pat.
`No. 5,340,433, Batchelder, et al. U.S. Pat. No. 5,402,351,
`Crumpet al. U.S. Pat. No. 5,503,785, Abramset al. U.S. Pat.
`No. 5,587,913, Danforth, et al. U.S. Pat. No. 5,738,817,
`Batchelder, et al. U.S. Pat. No. 5,764,521 and Combetal.
`US. Pat. No. 5,939,008, all of which are assigned to
`Stratasys, Inc., the assignee of the present invention. An
`extrusion head extrudes solidifiable material
`in a fluent
`
`strand (also termed a “bead”or “road’”’) from an extrusion tip
`onto a base. An extrusion head mayhave several extrusion
`tips in order to extrude different materials. For example, an
`extrusion head mayhavea first extrusion tip that extrudes
`modeling material to build up a three-dimensional model,
`and a second extrusiontip that extrudes support material to
`provide temporary support during a model build cycle. A
`base comprises a modeling substrate which is removably
`affixed to a modeling platform. The extruded material is
`deposited by the extrusiontip layer-by-layer in areas defined
`from the CAD model,as the extrusion head and the base are
`noved relative to each other by mechanical means in three
`dimensions. It is important to maintain a proper distance
`between the extrusion tip and the base while the model is
`being built to ensure proper construction of the model. If the
`extrusion tip is too far away from the base, then the build
`naterial may be misplaced or deformed. Conversely, if the
`extrusion tip is too close to the base, then it may contact the
`nodel and cause damage to the model and possibly the
`extrusion tip or head itself: Furthermore, it is important to
`ightly control the distance between extrusion tips in a
`nultiple tip system to ensure material layers are properly
`placed on the substrate or on top of one another.
`
`
`
`is removed from the
`the model
`[0005] Once finished,
`substrate. A solidifiable material which adheresto the pre-
`vious layer with an adequate bond uponsolidificationis used
`
`as the modeling material. Thermoplastic materials have been
`found particularly suitable for these deposition modeling
`techniques. Other additive process manufacturing tech-
`niques include depositing UVcurable polymers as in Mas-
`ters U.S.Pat. No. 5,46,569; jetting of droplets of material as
`in Helinski U.S. Pat. No. 5,50,515; extruding a settable
`plastic in vertical strips as in Valavaara U.S. Pat. No.
`4,749,347; laser welding deposition as in Pratt U.S. Pat. No.
`5,038,014; stacking and adhering planar elements as in
`DiMatteo U.S. Pat. No. 3,932,923; and applying shaped
`layers of paper as in Hull U.S. Pat. No. 5,82,559.
`
`rapid prototyping
`types of
`Several different
`[0006]
`machines are commercially available. This commercial
`availability makes three-dimensional modeling very conve-
`nient for consumers because they can create three-dimen-
`sional models right at
`their own facility. However,
`the
`machines also require servicing from time to time such as
`when an extrusion tip may become unusable or unreliable
`due to a back-up or solidification of modeling material
`inside the tip. When the flow of modeling material through
`the extrusion tip is obstructed installation of a new tip is
`typically necessary. Consumer-replaceable
`components
`within the rapid prototyping field have become more avail-
`able including replacement extrusion tips. While consumer-
`replaceable extrusion tips have made machine repairs more
`convenient, it also requires calibration ofthe tip once it has
`been replaced or
`re-installed. The calibration routine
`includescalibrating a Z-axis tip-to-substrate offset to ensure
`that the system knowsthe spatial relationship between the
`extrusion tip and the substrate prior to building a model.
`Furthermore, the calibration routine mayinclude calibrating
`
`
`an X-axis and Y-axis tip-to-origin offset to ensure that the
`system knowsthespatial relationship between the extrusion
`tip and anorigin on the substrate. If multiple tips exist, the
`calibration routine also includes a Z-axis tip-to-tip offset, an
`X-axis tip-to-tip offset, and a Y-axis tip-to-tip offset. Without
`calibration, the position of the extrusion tips relative to the
`base and relative to each other may be incorrect, which may
`result
`in the inability of the modeling system to build
`accurate, error-free models.
`
`
`
`[0007] Traditionally, calibration routines consisted of a
`manual or “eyeball” method performed bya trained con-
`sumer or technician. Previously,
`identifying any Z-axis
`tip-to-tip offset typically involved extruding layers of mate-
`rial and then manually measuring the thickness of the
`extruded material with a caliper. Similarly, identifying any
`X-axis or Y-axis tip-to-tip offset typically involved manually
`measuring the position of the extruded material along the
`X-Y axis. The tip-to-substrate offset 1s typically determined
`byetching a series of consecutive numbers into the substrate
`at increasing distances between the extrusion tip and the
`base and “eyeballing” the highest visible numberetched into
`the substrate. The tip-to-origin offset was typically cali-
`brated during assembly oraspart of an extrusion head gantry
`position calibration. Unfortunately, calibration routines
`involving manual or “eyeball” methods can be unreliable
`and time-consuming. Additionally, because proper manual
`
`calibration requires operator judgment, it can be difficult for
`
`
`
`inexperiencedusersto identify the correct calibrated offsets.
`
`Incorrect calibration of extrusion tips can result in
`[0008]
`the failure to form or build the three-dimensional model.
`
`17
`
`17
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`

`US 2007/0228592 Al
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`Oct. 4, 2007
`
`Therefore, there exists a need for an automatic extrusion tip
`calibration routine that does not require operator interven-
`tion or judgment.
`
`SUMMARYOF THE INVENTION
`
`[0009] The present invention is a method for performing a
`calibration routine in a three-dimensional modeling machine
`that builds-up three-dimensional objects as directed by a
`controller that deposits modeling material from a deposition
`device onto a substrate mounted on a platform. The method
`comprises generating a material build profile, which repre-
`sents a three-dimensionalstructure at a defined location. A
`
`relative position of the material build profile is then deter-
`nined. An expected build profile is identified and then
`comparedto the determinedrelative position of the material
`build profile to identify any difference therebetween from
`which an offset is determined. The modeling system then
`positions the deposition device based uponthe offset.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 13A is a top viewof analternative embodi-
`[0023]
`ment of a prefabricatedfixture.
`
`[0024]
`
`FIG. 13B isa sideviewofthe prefabricatedfixture.
`
`
`
` DETAILED DESCRIPTION
`
`
`FIG. 1 showsa generic representation of a three-
`[0025]
`dimensional modeling system 10, of a type known inthe art
`with which the present invention may be used. More spe-
`cifically, the three-dimensional modeling system 10 illus-
`trated in FIG. 1 is an extrusion-based layered modeling
`system. A computeraided design (CAD) program residentin
`processor 12 generatesa file describing the geometry of part
`14 to be created. A slicing program (shownasresident in
`processor 12, but which mayalternatively be resident in a
`separate processor) algorithmically subdividesthefile into
`modeling material volume elements 16 corresponding to
`shapes that can be extruded from a model material extrusion
`tip 38. Additional support material volume elements 18 are
`added as necessary to provide a mechanical support 45 to a
`model 47 of the part 14 during its construction.
`
`FIG. 1 is a schematic of a representative generic
`[0010]
`hree-dimensional layered modeling system.
`
`FIG. 2 is a process flow diagram illustrating the
`[0011]
`steps executed in performing a calibration routine according
`o the present invention.
`
`[0012] FIG.3 isa side view ofa support material extrusion
`tp of an extrusion-based layered modeling system of the
`present invention extruding a support pad of material.
`
`FIG.4 is a side viewof a model material extrusion
`[0013]
`tp of the extrusion-based layered modeling system of the
`present invention extruding a model pad of material.
`
`[0026] Modeling system 10 utilizes a pair of dispensers 38
`and 40, to dispense the different materials used to construct
`model 47 and support 45. In this embodiment, each dis-
`penser includes its own discharge tip, such that modeling
`system 10 includes model material extrusion tip 38 which
`extrudes modeling material, and support material extrusion
`tip 40, which extrudes support material. Modeling material
`is dispensed by tip 38 to build the object or model 47 based
`on the modeling material volume elements 16, while support
`material
`is dispensed by tip 40 to form the underlying
`support 45 based on the support material volume elements
`18. The support structure 45 is later removed after sufficient
`solidification of the modeling material
`that created the
`model 47.
`[0014] FIG.5is a perspective view of a preferred embodi-
`
`nent of a sensor assembly of the present invention with a
`[0027] Upon receiving three-dimensional shape data from
`plunger in the lowered position, mounted to an extrusion
`processor 12 over line 20, controller 24 controls the extru-
`ead of the extrusion-based layered modeling system and
`sion of modeling material and support material in an XYZ-
`positioned over the model pad and the support pad.
`coordinate reference frame. Beads of modeling material and
`support material are extruded layer-by-layerin a build path
`that is a pattern defined by the modeling material volume
`elements 16 and support material volume elements 18.
`Controller 24 determines and maintains
`in associated
`
`
`
`FIGS. 6Aand 6B depict the loweringof the plunger
`[0015]
`0 a sensing position.
`
`FIGS. 7A and 7B depict the raising of the plunger
`[0016]
`0 a stored position.
`
`FIG. 8A is a cross-sectional view of the sensor
`[0017]
`assembly of FIG. 5, with the plunger in contact with the
`nodel pad.
`
`FIG. 8B is a cross-sectional view of the sensor
`[0018]
`assembly of FIG. 5, with the plunger occluding an optical
`sensor.
`
`FIG. 9 is a perspective view of an alternative
`[0019]
`embodimentof the sensor assembly ofthe present invention.
`
`FIG. 10 is a side view of the sensor assembly of
`[0020]
`FIG. 9 sensing a side surface of the model pad and the
`support pad.
`
`FIG. 11 is a top view of the model pad and the
`[0021]
`support pad on a substrate.
`
`FIG. 12 is a process flow diagram illustrating the
`[0022]
`steps executed in sensing a surface of an object by the
`nodeling system.
`
`memory 22 data representative of movements required to
`build the model 47 accordingto the build path for eachlayer.
`Based on this data, controller 24 sends control signals to
`X-Y axis translator 26, Z-axis translator 30, and extrusion
`pump 34 over output signal lines 28a, 285 and 28c, respec-
`tively, to create the particular layer according to the build
`path. X-Y axis translator 26 is an electromechanical device
`that moves robotic arm 42 accordingto the build path for the
`particular layer. Extrusion pump 34 synchronously provides
`modeling material and support material from material sup-
`ply 32 to extrusion head 36 and ultimately deposited by
`model material extrusion tip 38 and support material extru-
`sion tip 40, respectively.
`
`[0028] The model 47 and support 45 are built on top of
`substrate 48. Substrate 48 is removably mounted on mod-
`eling platform 46 and is located in modeling envelope 44.
`Modeling platform 46 moves in a Z-direction under the
`control of Z-axis translator 30. The Z-axis as shown is
`oriented radially away from the earth’s surface. In other
`implementations, however, it can be towards the ground or
`
`18
`
`18
`
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`

`US 2007/0228592 Al
`
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`
`at some other chosen angle. Z-axis translator 30 incremen-
`tally lowers modeling platform 46 following deposition of a
`layer of modeling material or support material, to build up
`model 47 and support structure 45 layer-by-layer on sub-
`strate 48. After model 47 is created,
`it along with any
`corresponding support elements 45 are removed from mod-
`eling system 10 and from substrate 48.
`
`[0029] Modeling system 10 builds precise and accurate
`nodels 47 by controlling the height and position of each
`layer that is built. Typically, modeling system 10 controls the
`rate that material is deposited from the deposition device to
`create each layer with a constant height. In this exemplary
`embodiment, the position of the tip depositing the material
`is important to ensure material is deposited and layers are
`built according to the build path in the proper locations. If
`he actual positions of the tips are not the same as the
`positions expected by controller 24, the layers of material
`will not be accurately extruded in the proper X-Y-Z posi-
`ons.
`
`[0030] The tip position is also very important in control-
`ling the height of each build layer in the Z-direction. The
`bottom of the extrusion tip typically includes an “iron”that
`physically contacts and flattens out the bead of material
`naking up the build path for that layer as it is deposited. If
`he tip extruding material is positioned too high above the
`surface that the material is being deposited upon, then the
`iron will not flatten out as much of the bead of material as
`expected resulting in the beadand layer height being greater
`han desired and not constant. Conversely,if the tip extrud-
`ing material is too low,thenthe iron will flatten out too much
`of the bead of material resulting in a bead and layer height
`hat is less than desired as well as potentially clogging the
`extrusion tip. Inconsistent bead heights within a build layer
`results in inconsistent layer heights which are propagated
`hroughout the build cycle as the model 47is being created.
`This results in errors and structural deficiencies in the model
`47. It is importantto the construction of accurate models 47
`hat the thickness and position of each layer be closely
`controlled.
`
`
`
`[0031] Based uponthe above discussion,it is apparent that
`in order to build accurate models, it is necessary to tightly
`control the X-Y position and the Z-axis height of a material
`bead. The present invention employs an automatic tip cali-
`bration capable of calibrating an extrusion tip in the X, Y,
`and Z directions in order to build precise and accurate
`nodels. For purposes of example and clarity of the inven-
`ion, the following discussion will focus first on the calibra-
`ion of oneor more extrusiontips in the Z-direction, and then
`on the calibration in the X and Y directions.
`
`[0032] Considering the Z-direction, the position ofthe tip
`extruding the material in relation to the surface upon which
`he material will be deposited must be controlled and
`naintained at a desired level in order to control the build
`layer thickness. This is accomplished byprecisepositioning
`of the extrusion tip with respect to the substrate 48 upon
`which the extrusiontip will initially deposit material. Once
`he extrusion tip is properly positioned in relation to the
`substrate 48,
`then precise control of movement of the
`platform 46, and hence the substrate 48, by the 7-axis
`ranslator 30 as well as the head 36 by the X-Y axis
`ranslator 26 is required. Upon completion ofdepositing one
`layer of the model 47 and support 45, the Z-axis translator
`
`30 will lower the platform 46 a distance equal to the height
`of the next layer of material. This controlled movement will
`ensure that the extrusion tip remains positioned properly
`with respect
`to the surface upon which it will deposit
`material. The distance between the extrusion tip and the
`substrate 48 must therefore be determined along with any
`necessary offset to adjust the position of the platform 46 to
`attain the desired distance between the substrate 48 and the
`extrusion tip. The difference between the Z-axis position of
`the extrusion tip and the substrate represents a Z-axis
`tip-to-substrate offset for that particular extrusion tip.
`
`[0033] Modeling system 10 mayinclude multiple extru-
`sion tips as illustrated in FIG. 1. Typically, modeling system
`10 includes only one extrusion position and toggles the
`multiple extrusion tips between a higher stored, or non-
`extruding position, and the lower extrusion position as
`explained in U.S. Pat. No. 5,503,785. As with a singletip,
`each of the multiple tips also must be positioned an equal
`distance from the surface upon whichthey will deposit their
`respective materials when theyare in the extrusion position.
`However,until properlycalibrated, the relative Z-axis posi-
`tionsof the tips may vary when eachofthedifferenttips are
`in the extrusion position. This difference should be
`accounted for andthe position ofthe platform 46 adjusted to
`position each of the multiple tips an equal distance from the
`
`surface upon which they will deposit their respective mate-
`
`
`rial. The difference between the Z-axis position of the tips
`represents a Z-axis tip-to-tip offset value. The tip-to-tip
`offset value represents the adjustment necessary to the
`positionor height of the platform 46 in order to position the
`tips the same distance away from the surface upon which
`they will deposit material.
`
`
`
`[0034] The present invention relies upon the ability of the
`modeling system 10 to create constant height bead layers
`and to properly position the platform 46 to calibrate the
`position of the extrusion tips in relation to a reference point,
`such asthe substrate, and any otherextrusiontips. FIG. 2 is
`a flowchart of a tip calibration method 100 according to the
`present invention. For purposes of example, the calibration
`method 100 will now be described with reference to a Z-axis
`tip calibration. However,
`it should be understood that an
`X-axis and a Y-axistip calibration mayalso be performed by
`application of calibration method 100, as will be described
`in more detail later.
`
`[0035] The method 100 begins by generating a material
`build profile in step 102. The material build profile may
`either be generated by the modeling system 10 with the
`particular extrusion tip that is being calibrated or byplacing
`a prefabricated structure on the platform 46. In this example,
`the material build profile is a structure having a defined
`shape and size created from the material deposited by the
`extrusion tip. The defined shape and size of the material
`build profile results in defined lengths, widths, and heights
`for the structure thatis built at a defined andprecise location.
`
`[0036] Once the material build profile is created, its rela-
`tive position which mayrepresent a dimensionor a specific
`location is determined in step 104. The relative position of
`the material build profile in this example is determined by
`measuring the height of the structure relative to a reference
`point, such as the substrate 48, at specific defined locations.
`
`[0037] An expectedbuild profile is identified in step 106.
`The expected build profile represents the dimension or
`
`19
`
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`

`US 2007/0228592 Al
`
`Oct. 4, 2007
`
`location that should be obtained for the relative position of
`he material build profile if the tip is properly calibrated. In
`his example, the expected build profile may beidentified by
`relying on the ability of the modeling system 10 to generate
`layers of material with a constant height.
`
`[0038] The expected build profile for a Z-axis tip-to-
`substrate calibration may beeither provided as an inputto or
`calculated by the controller 24. For instance, an expected
`build profile (such as a height) may be inputted to the
`controller 24 from either the processor 12 or memory 22.
`The controller 24 may also calculate the expected build
`profile by multiplying the constant height value for each
`layer generated by the modeling system 10 by the number of
`layers that would be required to create the material build
`profile according to tts defined shape andsize.
`
`
`
`3, the support material extrusion tip 40 is depositing a top or
`final layer 50 of support material 41 to construct the pad 49.
`[0042] Upon completing the construction of pad 49, or the
`material build profile, the relative position of the pad 49, or
`step 104, is determined in the X, Y, or Z axis to calibrate
`along that respective axis. In this example, the Z-axis is
`being calibrated and so the height of the pad 49, which
`represents the material build profile, is determined to be a
`height H1.
`[0043] The height of the expected build profile is identi-
`
`fied next in step 106. The expected build profile is identified
`as height E in FIG.3. In this instance, height E is determined
`bycalculating the product of the constant layer height value
`that
`the modeling system 10 deposits material and the
`numberof layers required to build the pad 49, which in this
`case is five layers. The constant layer height value of the
`[0039] Alternatively, the expected build profile for a tip-
`modeling system 10 equals the theoretical height of each
`o-tip calibration may be identified by determining the
`layer according to the slicing program.
`relative position of a secondstructure. The second structure
`[0044]
`Asillustrated in FIG.3, in this example the height
`nay be either prefabricated or created by a second deposi-
`
`H Jisless than the heightE bythe distance A. This indicates
`ion device or, in this case, a second extrusion tip. In the case
`that the support extrusion
`tip 40 is too low or close to the
`ofa tip-to-tip calibration, the expected build profile could be
`substrate 48 and as a result, the support material extrusion
`identified by measuringarelative position, such as a height,
`tip 40 plowed through the support material 41 while creating
`of the second structure having the same defined shape and
`the pad 49 and lowered or reduced the height of the build
`size and created according to the same build path as the
`layers comprising the pad 49. The distance A is used to
`original material build profile, but at a different defined
`determine or derive the offset necessary to properly position
`location. The secondstructure would also be created bythe
`the tip 40 with respect to the substrate 48, or the Z-axis
`other extrusion tip that
`is the subject of the tip-to-tip
`tip-to-substrate offset for the tip 40. Once the tip 40 has been
`calibration.
`properly positioned with respect
`to the substrate 48 by
`accounting for the offset correspondingto the distanceA,tip
`40 has been calibrated with respect to substrate 48, or the
`Z-axis tip-to-substrate calibration has been completed. In
`this embodiment, the calibration routine 100 determines the
`Z-axis tip-to-substrate offset within a tolerance of about
`0.0005 inches.
`
`
`
`
`
`
`[0040] After the expected build profile is identified, then
`he material build profile is compared to the expected build
`profile in step 108 to identify anyoffset that may exist. The
`offset may be identified as either the difference between or
`determined from the material build profile and the expected
`build profile when those values are compared. Forinstance,
`if
`the extrusion tip is too low or close to the substrate 48
`whentheinitial layer is deposited, the extrusion tip will iron
`he material being deposited such that the height of the
`naterial build profile will be less than the constant height
`valueof the layer of material when the modeling system 10
`is operating and calibrated properly. The offset represents
`he adjustment necessaryto properly position the extrusion
`ip that created the material build profile with respect to the
`
`substrate 48 carried by the platform 46. This adjustment of
`
`
`
`he extrusion tip position taking into account the offset is
`performed in step 110. In this instance where the extrusion
`ip is too low or close to the substrate 48, the modeling
`system 10 would lower the platform 46 an amount equal to
`or derived from the offset to properly position the extrusion
`
`ip with respect to the substrate 48. The modeling system 10
`
`would also record orstore the offset value in memory 22 to
`properly position the extrusion tip on subsequent builds.
`
`FIG. 3 is a side view illustrating the support
`[0041]
`naterial extrusion tip 40 depositing, in this example, support
`naterial 41 on top of substrate 48. Support material 41 is
`shownwith a broken line through its center to distinguish the
`support material 41 from the build material 43 in FIG.4. The
`nodeling system 10 deposits support material 41 with
`support material extrusion tip 40 according to a defined
`build path to generate the material build profile of step 102
`in method 100. The material build profile illustrated in FIG.
`3 is referred to as a pad 49. The pad 49 is in a geometric
`shape of a rectangle as shown in FIG. 5. As shownin FIG.
`
`[0045] Upon completing the Z-axis tip-to-substrate cali-
`bration, the modeling system 10 is able to build accurate
`models 47 or supports 45 with the tip 40. If the modeling
`system 10 includes only one extrusion tip, then the Z-axis
`calibration of the extrusion tip is completed. However, if the
`modeling system 10 includes more than one extrusiontip,
`then the remaining extrusion tips also require calibration.
`[0046] When the modeling system 10 includes multiple
`extrusion tips, it will typically toggle the extrusion tip that
`will deposit the desired material for that build path into the
`extrusion position from its stored or non-extrudingposition.
`The extrusion position is generally lower than the stored or
`non-extruding position. This difference in tip position
`between the extruding position and stored or non-extrusion
`positionis illustrated by comparing therelative positions of
`tips 38 and 40 in FIGS. 3 and 4. In FIG.3, tip 40 has been
`toggled by controller 24 into the extrusion position which is
`lower than the stored or non-extrusion position oftip 38.
`Conversely, in FIG. 4, controller 24 has toggledtip 38 into
`the extrusion position which is lower than the stored or
`non-extruding position ofthe tip 40. Bypositioningthe tip
`which is not depositing material in a higher stored position,
`the modeling system 10 ensures there is adequate clearance
`to deposit material out of the other tip and avoid the
`non-depositing tip from contacting or plowing into the
`deposited material.
`[0047]
`Ina multiple tip modeling system 10, the tip that
`will deposit material first is generally used to perform the
`
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`US 2007/0228592 Al
`
`Oct. 4, 2007
`
`Z-axis tip-to-substrate calibration. This will ensure that the
`initial layer of deposited material will begin correctly. Typi-
`cally, the modeling system 10 will deposit a base of support
`material 41 atop substrate 48 and then build model 47 on top
`of the base. Creating a base of support material 41 will
`facilitate separation of the model 47 from the substrate 48
`without damageto the model 47. While each tip ina multiple
`tip modeling system 10 could be calibrated to the substrate,
`it is also preferable to calibrate one tip to another with a
`Z-axis tip-to-tip calibration.
`
`FIG. 4 illustrates the method 100 of the present
`[0048]
`invention for a Z-axis tip-to-tip calibration. As shown in
`FIG. 4, material extrusion tip 38 has been toggled into the
`extrusion position to deposit build material 43 while support
`extrusion tip 40 has been toggled to a stored or non-
`extruding position. Material extrusion tip 38 deposits build
`naterial 43 in the defined shape and sizeat a precise location
`© generate the material build profile of step 102. Again, in
`his example, the modeling system 10 generates a pad 51
`similar to the pad 49, except that pad 51 is constructed with
`build material 43 rather than support material 41 like the pad
`49. As shownin FIG.4, the tip 38 is depositing a last layer
`or top layer 52 of build material 43 to create pad 51, or the
`naterial build profile for this calibration.
`
`
`
`O