U.S. patent application number 16/053496 was filed with the patent office on 2018-12-06 for mold lock remediation.
The applicant listed for this patent is Desktop Metal, Inc.. Invention is credited to Ricardo Chin, Blake Z. Reeves.
Application Number | 20180348739 16/053496 |
Document ID | / |
Family ID | 62143563 |
Filed Date | 2018-12-06 |
United States Patent
Application |
20180348739 |
Kind Code |
A1 |
Chin; Ricardo ; et
al. |
December 6, 2018 |
MOLD LOCK REMEDIATION
Abstract
Mold lock is remediated by performing a layer-by-layer,
two-dimensional analysis to identify unconstrained removal paths
for any support structure or material within each two-dimensional
layer, and then ensuring that aligned draw paths are present for
all adjacent layers, all as more specifically described herein.
Where locking conditions are identified, a sequence of modification
rules are then applied, such as by breaking support structures into
multiple, independently removable pieces. By addressing mold lock
as a series of interrelated two-dimensional geometric problems, and
reserving three-dimensional remediation strategies for more
challenging, complex mold lock conditions, substantial advantages
can accrue in terms of computational speed and efficiency.
Inventors: |
Chin; Ricardo; (Shrewsbury,
MA) ; Reeves; Blake Z.; (Chelsea, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Desktop Metal, Inc. |
Burlington |
MA |
US |
|
|
Family ID: |
62143563 |
Appl. No.: |
16/053496 |
Filed: |
August 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15960042 |
Apr 23, 2018 |
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16053496 |
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62489271 |
Apr 24, 2017 |
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62580966 |
Nov 2, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G05B 2219/49007
20130101; B33Y 50/00 20141201; B29C 64/386 20170801; H04N 1/4092
20130101; G05B 19/4099 20130101; B22F 3/1055 20130101; B33Y 50/02
20141201; B28B 1/001 20130101; B33Y 10/00 20141201; B22F 2003/1057
20130101; B28B 17/0081 20130101; B29C 64/40 20170801; B29C 64/10
20170801; G05B 2219/35134 20130101 |
International
Class: |
G05B 19/4099 20060101
G05B019/4099; B28B 1/00 20060101 B28B001/00; B22F 3/105 20060101
B22F003/105; B33Y 50/02 20150101 B33Y050/02; B28B 17/00 20060101
B28B017/00 |
Claims
1. A method comprising: receiving a digital model including a raft,
an object for fabrication on the raft, and a support for
fabrication with the object to provide physical support according
to one or more design rules; dividing the digital model into a
number of layers formed by planar, horizontal cross sections
through the digital model; for each layer, identifying one or more
draw paths for separating a layer of support formed by a cross
section of the support from a layer of the object formed by a cross
section of the object within the layer of the digital model;
identifying one of the number of layers as a locked layer when the
layer of support has no draw path for separating the layer of
support from the layer of the object, or when the layer of support
is vertically coupled to a second layer of the support having no
draw path in common with the layer of support; identifying a mold
locked region of the support including the locked layer and any
vertically contiguous support layers; dividing the mold locked
region with one or more vertical planes into one or more
subregions; if the one or more subregions can be horizontally
removed, processing a remaining digital model, excluding the one or
more subregions, for mold lock remediation; and if the one or more
subregions cannot be horizontally removed, employing one or more
three-dimensional remediation strategies to address the mold locked
region.
2. The method of claim 1 wherein dividing the mold locked region
includes iteratively attempting an increasing number of planar
slices until the one or more subregions can be horizontally removed
or a threshold is reached.
3. The method of claim 1 wherein the one or more three-dimensional
remediation strategies includes vertically moving the mold locked
region after a second mold locked region is removed from a
vertically adjacent volume.
4. The method of claim 1 wherein the one or more three-dimensional
remediation strategies includes subdividing the mold locked region
into a number of volumetric subregions and searching for
three-dimensional draw paths for removing the volumetric subregions
from the object.
5. The method of claim 4 wherein the volumetric subregions are
sized for removal through an opening in the object.
6. The method of claim 1 further comprising, if the one or more
three-dimensional remediation strategies fail to remediate the mold
locked region, providing a notification to a user of an
unremediated mold lock condition.
7. The method of claim 1 wherein the draw path includes a range of
angles over which a first rigid shape of the cross section of the
support can be separated in a straight line from a second rigid
shape of the object.
8. The method of claim 1 wherein identifying one or more draw paths
includes testing for linear separation in a straight line at a
number of discrete angles over a predetermined range of angles.
9. The method of claim 1 further comprising performing an initial
check to determine whether the object can be separated from the
support along a vertical axis.
10. The method of claim 1 further comprising separating regions of
the support touching the raft from regions of the support not
touching the raft along a vertical axis and performing a check to
determine whether the object can be separated from the support
along the vertical axis.
11. The method of claim 1 further comprising fabricating the object
and the support based on the digital model.
12. The method of claim 11 wherein fabricating includes fabricating
an interface layer between the one or more subregions of the mold
locked region.
13. The method of claim 11 wherein fabricating the object includes
fabricating an interface layer between the support and the
object.
14. The method of claim 1 wherein the design rules include
fabrication design rules.
15. The method of claim 1 wherein the design rules include
sintering design rules.
16. The method of claim 1 wherein the number of layers correspond
to material deposition layers for an additive fabrication process.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/960,042 filed on Apr. 23, 2018, which
claims priority to U.S. Prov. App. No. 62/580,966 filed on Nov. 2,
2017 and U.S. Prov. App. No. 62/489,271 filed on Apr. 24, 2017. The
entire content of each of the foregoing applications is hereby
incorporated by reference.
FIELD
[0002] This disclosure relates to three-dimensional fabrication,
and more specifically to techniques for remediating mold lock in a
three-dimensional fabrication process.
BACKGROUND
[0003] Mold lock occurs in three-dimensional printing when rigid
support structures for a printed object are geometrically
interlocked with the object in a manner that provides no physical
draw path for removal of the supports. There remains a need for
techniques that automatically identify and remediate mold lock
conditions within three-dimensional models of printed objects.
SUMMARY
[0004] Mold lock is remediated by performing a layer-by-layer,
two-dimensional analysis to identify unconstrained removal paths
for any support structure or material within each two-dimensional
layer, and then ensuring that aligned draw paths are present for
all adjacent layers, all as more specifically described herein.
Where locking conditions are identified, a sequence of modification
rules are then applied, such as by breaking support structures into
multiple, independently removable pieces. By addressing mold lock
as a series of interrelated two-dimensional geometric problems, and
reserving three-dimensional remediation strategies for more
challenging, complex mold lock conditions, substantial advantages
can accrue in terms of computational speed and efficiency.
[0005] In one aspect, a method disclosed herein may include
receiving a digital model including a raft, an object for
fabrication on the raft, and a support for fabrication with the
object to provide physical support according to one or more design
rules; dividing the digital model into a number of layers formed by
planar, horizontal cross sections through the digital model; for
each layer, identifying one or more draw paths for separating a
layer of support formed by a cross section of the support from a
layer of the object formed by a cross section of the object within
the layer of the digital model; identifying one of the number of
layers as a locked layer when the layer of support has no draw path
for separating the layer of support from the layer of the object,
or when the layer of support is vertically coupled to a second
layer of the support having no draw path in common with the layer
of support; identifying a mold locked region of the support
including the locked layer and any vertically contiguous support
layers; dividing the mold locked region with one or more vertical
planes into one or more subregions; if the one or more subregions
can be horizontally removed, processing a remaining digital model,
excluding the one or more subregions, for mold lock remediation;
and if the one or more subregions cannot be horizontally removed,
employing one or more three-dimensional remediation strategies to
address the mold locked region.
[0006] Dividing the mold locked region may include iteratively
attempting an increasing number of planar slices until the one or
more subregions can be horizontally removed or a threshold is
reached. The one or more three-dimensional remediation strategies
may include vertically moving the mold locked region after a second
mold locked region is removed from a vertically adjacent volume.
The one or more three-dimensional remediation strategies may
include subdividing the mold locked region into a number of
volumetric subregions and searching for three-dimensional draw
paths for removing the volumetric subregions from the object. The
volumetric subregions may be sized for removal through an opening
in the object. The method may further include, if the one or more
three-dimensional remediation strategies fail to remediate the mold
lock, providing a notification to a user of an unremediated mold
lock condition. The draw path may include a range of angles over
which a first rigid shape of the cross section of the support can
be separated in a straight line from a second rigid shape of the
object. Identifying one or more draw paths may include testing for
linear separation in a straight line at a number of discrete angles
over a predetermined range of angles. The method may further
include performing an initial check to determine whether the object
can be separated from the support along a vertical axis. The method
may further include separating regions of the support touching the
raft from regions of the support not touching the raft along a
vertical axis and performing a check to determine whether the
object can be separated from the support along the vertical axis.
The method may further include fabricating the object and the
support based on the digital model. Fabricating the object and the
support may include fabricating an interface layer between the one
or more subregions of the mold locked region. Fabricating the
object and the support may include fabricating an interface layer
between the support and the object. The design rules may include
fabrication design rules. The design rules may include sintering
design rules. The number of layers may correspond to material
deposition layers for an additive fabrication process.
[0007] In one aspect, a computer program product disclosed herein
may include computer executable code embodied in a non-transitory
computer readable medium that, when executing on one or more
computing devices, performs the steps of receiving a digital model
including a raft, an object for fabrication on the raft, and a
support for fabrication with the object to provide physical support
according to one or more design rules; dividing the digital model
into a number of layers formed by planar, horizontal cross sections
through the digital model; for each layer, identifying one or more
draw paths for separating a layer of support formed by a cross
section of the support from a layer of the object formed by a cross
section of the object within the layer of the digital model;
identifying one of the number of layers as a locked layer when the
layer of support has no draw path for separating the layer of
support from the layer of the object, or when the layer of support
is vertically coupled to a second layer of the support having no
draw path in common with the layer of support; identifying a mold
locked region of the support including the locked layer and any
vertically contiguous support layers; dividing the mold locked
region with one or more vertical planes into one or more
subregions; if the one or more subregions can be horizontally
removed, processing a remaining digital model, excluding the one or
more subregions, for mold lock remediation; and if the one or more
subregions cannot be horizontally removed, employing one or more
three-dimensional remediation strategies to address the mold locked
region.
[0008] The computer program product may further include code that
performs the step of performing an initial check to determine
whether the object can be separated from the support along a
vertical axis. The computer program product may further include
code that performs the step of separating regions of the support
touching the raft from regions of the support not touching the raft
along a vertical axis and performing a check to determine whether
the object can be separated from the support along the vertical
axis. The computer program product may further include code that
generates instructions executable by a three-dimensional printer to
fabricate the object and the support, including fabricating an
interface layer between the object and the support and a second
interface layer between the one or more subregions of the mold
locked region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing and other objects, features and advantages of
the devices, systems, and methods described herein will be apparent
from the following description of particular embodiments thereof,
as illustrated in the accompanying drawings. The drawings are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the devices, systems, and methods
described herein.
[0010] FIG. 1 shows an additive manufacturing system.
[0011] FIG. 2 shows a method for fabricating an object.
[0012] FIG. 3 shows a mold lock condition in a fabricated
object.
[0013] FIG. 4 shows a flow chart of a method for remediating mold
lock conditions.
[0014] FIG. 5 illustrates an object and support that have been
processed to remediate mold lock.
DESCRIPTION
[0015] Embodiments will now be described with reference to the
accompanying figures. The foregoing may, however, be embodied in
many different forms and should not be construed as limited to the
illustrated embodiments set forth herein.
[0016] All documents mentioned herein are incorporated by reference
in their entirety. References to items in the singular should be
understood to include items in the plural, and vice versa, unless
explicitly stated otherwise or clear from the context. Grammatical
conjunctions are intended to express any and all disjunctive and
conjunctive combinations of conjoined clauses, sentences, words,
and the like, unless otherwise stated or clear from the context.
Thus, the term "or" should generally be understood to mean "and/or"
and so forth.
[0017] Recitation of ranges of values herein are not intended to be
limiting, referring instead individually to any and all values
falling within the range, unless otherwise indicated herein, and
each separate value within such a range is incorporated into the
specification as if it were individually recited herein. The words
"about," "approximately," or the like, when accompanying a
numerical value, are to be construed as indicating a deviation as
would be appreciated by one of ordinary skill in the art to operate
satisfactorily for an intended purpose. Ranges of values and/or
numeric values are provided herein as examples only, and do not
constitute a limitation on the scope of the described embodiments.
The use of any and all examples, or exemplary language ("e.g.,"
"such as," or the like) provided herein, is intended merely to
better illuminate the embodiments and does not pose a limitation on
the scope of the embodiments or the claims. No language in the
specification should be construed as indicating any unclaimed
element as essential to the practice of the embodiments.
[0018] In the following description, it is understood that terms
such as "first," "second," "top," "bottom," "up," "down," "above,"
"below" and the like, are words of convenience and are not to be
construed as limiting terms unless specifically stated to the
contrary.
[0019] FIG. 1 shows an additive manufacturing system for use with
sinterable build materials. The system 100 may include a printer
102, a conveyor 104, and a post-processing station 106.
[0020] In general, the printer 102 may be any of the printers
described herein or any other three-dimensional printer suitable
for adaptation to fabrication with sinterable build materials. By
way of non-limiting example, the printer 102 may include a fused
filament fabrication system, a binder jetting system, a
stereolithography system, a selective laser sintering system, or
any other system that can be usefully adapted to form a net shape
object under computer control using the sinterable build materials
contemplated herein.
[0021] The output of the printer 102 may be an object 103 that is a
green body or the like formed of a build material including any
suitable powder (e.g., metal, metal alloy, ceramic, and so forth,
as well as combinations of the foregoing), along with a binder that
retains the powder in a net shape produced by the printer 102. A
wide range of compositions may be employed as the build material
contemplated herein. For example, powdered metallurgy materials or
the like may be adapted for use as a build material in a fused
filament fabrication process or the like. Metal injection molding
materials with suitable thermo-mechanical properties for extrusion
in a fused filament fabrication process are described by way of
non-limiting example in Heaney, Donald F., ed. "Handbook of Metal
Injection Molding" (2012), the entire contents of which are hereby
incorporated by reference.
[0022] The conveyor 104 may be used to transport the object 103
from the printer 102 to a post-processing station 106, which may
include one or more separate processing stations, where debinding
and sintering can be performed. The conveyor 104 may be any
suitable mechanism or combination of devices suitable for
physically transporting the object 103. This may, for example,
include robotics and a machine vision system or the like on the
printer side for detaching the object 103 from a build platform, as
well as robotics and a machine vision system or the like on the
post-processing side to accurately place the object 103 within the
post-processing station 106. In another aspect, the post-processing
station 106 may serve multiple printers so that a number of objects
can be debound and sintered concurrently, and the conveyor 104 may
interconnect the printers and post-processing station so that
multiple print jobs can be coordinated and automatically completed
in parallel. In another aspect, the object 103 may be manually
transported between the two corresponding stations.
[0023] The post-processing station 106 may be any system or
combination of systems useful for converting a green part formed
into a desired net shape from a metal injection molding build
material by the printer 102 into a final object. The
post-processing station 106 may, for example, include a debinding
station such as a chemical debinding station for dissolving binder
materials in a solvent or the like, or more generally any debinding
station configured to remove at least a portion of the binder
system from the build material of the object 103. The
post-processing station 106 may also or instead include a thermal
sintering station for applying a thermal sintering cycle at a
sintering temperature for the build material, or the powdered
material in the build material, such as a sintering furnace
configured to sinter the powdered material into a densified object.
The components of the post-processing station 106 may be used in
sequence to produce a final object. As another example, some
contemporary injection molding materials are engineered for thermal
debinding, which makes it possible to perform a combination of
debinding and sintering steps with a single oven or similar device.
In general, the thermal specifications of a sintering furnace will
depend upon the powdered material, the binder system, the volume
loading of the powdered material into the binder system, and other
aspects of the green object and the materials used to manufacture
same. Commercially available sintering furnaces for thermally
debound and sintered metal injection molding (MIM) parts will
typically operate with an accuracy of +/-5 degrees Celsius or
better, and at temperatures of at least 600 degrees Celsius, or
from about 200 degrees Celsius to about 1900 degrees Celsius for
extended times. Any such furnace or similar heating device may be
usefully employed as the post-processing station 106 as
contemplated herein. Vacuum or pressure treatment may also or
instead be used. In an aspect, after the object 103 is placed in
the oven, beads of an identical or similar composition, with the
addition of an unsinterable exterior coating, may be packed into
the oven with the object to provide general mechanical support with
a thermally matched shrinkage rate that will not form a bond to the
object during sintering.
[0024] In the context of this description, it will be appreciated
that sintering may usefully include different types of sintering.
For example, sintering may include the application of heat to
sinter an object to full density or nearly full density. In another
aspect, sintering may include partial sintering, e.g., for a
sintering and infiltration process in which pores of a partially
sintered part are filled, e.g., through contact and capillary
action, with some other material such as a low melting point metal
to increase hardness, increase tensile strength, or otherwise alter
or improve properties of a final part. Thus, any references herein
to sintering should be understood to contemplate sintering and
infiltration unless a different meaning is expressly stated or
otherwise clear from the context. Similarly, references to a
sinterable powder or sinterable build material should be understood
to contemplate any sinterable material including powders that can
be sintered and infiltrated to form a final part.
[0025] It will also be appreciated that a wide range of other
debinding and sintering processes can be used. For example, the
binder may be removed in a chemical debind, thermal debind, or some
combination of these. Other debinding processes are also known in
the art, such as supercritical debinding or catalytic debinding,
any of which may also or instead be employed by the post-processing
station 106. For example, in a common process, a green part is
first debound using a chemical debind, which is following by a
thermal debind at a moderately high temperature (in this context,
around 700-800 Celsius) to remove organic binder and create enough
necks among a powdered material to provide sufficient strength for
handling. From this stage, the object may be moved to a sintering
furnace to remove any remaining components of a binder system and
densify the object into a final part. In another aspect, a pure
thermal debind may be used to remove the organic binder. More
generally, any technique or combination of techniques may be
usefully employed to debind an object as contemplated herein.
[0026] The post-processing station 106 may be optimized in a
variety of ways for use in an office environment. In one aspect,
the post-processing station 106 may include an inert gas source
108. The inert gas source 108 may, for example, include argon or
other inert gas (or other gas that is inert to the sintered
material), and may be housed in a removable and replaceable
cartridge that can be coupled to the post-processing station 106
for discharge into the interior of the post-processing station 106,
and then removed and replaced when the contents are exhausted. The
post-processing station 106 may also or instead include a filter
110 such as a charcoal filter or the like for exhausting gasses
that can be outgassed into an office environment in an unfiltered
form. For other gasses, an exterior exhaust, or a gas container or
the like may be provided to permit use in unventilated areas. For
reclaimable materials, a closed system may also or instead be used,
particularly where the environmental materials are expensive or
dangerous.
[0027] In one aspect, the post-processing station 106 may be
coupled to other system components. For example, the
post-processing station 106 may include information from the
printer 102, or from a controller for the printer, about the
geometry, size, mass, and other physical characteristics of the
object 103 in order to generate a suitable debinding and sintering
profile. In another aspect, the profile may be independently
created by the controller or other resource and transmitted to the
post-processing station 106 when the object 103 is conveyed. In
another aspect, the post-processing station 106 may monitor the
debinding and sintering process and provide feedback, e.g., to a
smart phone or other remote device 112, about a status of the
object 103, a time to completion, and other processing metrics and
information. The post-processing station 106 may include a camera
114 or other monitoring device to provide feedback to the remote
device 112, and may provide time lapse animation or the like to
graphically show sintering on a compressed time scale.
Post-processing may also or instead include finishing with heat, a
hot knife, tools, or similar. Post-processing may include applying
a finish coat.
[0028] In another aspect, the post-processing station 106 may be
remote from the printer 102, e.g., in a service bureau model or the
like where the object 103 is fabricated and then sent to a service
bureau for outsourced debinding, sintering and so forth. Thus, for
any of the support structures, interface layers, and so forth
described below, or more generally, for any fabricated items
described below, this disclosure expressly contemplates a
corresponding method of receiving an object or item containing any
such features, e.g., any features or structures described below,
and then performing one or more post-processing steps including but
not limited to shaping, debinding, sintering, finishing, assembly,
and so forth. This may, for example, include receiving a green part
with a fully intact binder system, at a remote processing resource,
where the part can be debound and sintered at the remote processing
resource. This may also or instead include receiving a brown part
where some or all of the binder system has been removed in a
debinding process at another location and the part is only sintered
at the remote processing resource. In this latter case, a portion
of the binder system may usefully be retained in the part, either
as a backbone binder to retain a shape of the object during
sintering until a self-supporting sintering strength is achieved,
or as a residual primary binder that is left in the part to improve
structural integrity during shipping or other handling.
[0029] More generally, this disclosure contemplates any combination
and distribution of steps suitable for centralized or distributed
processing into a final part, as well as any intermediate forms of
the materials, articles of manufacture, and assemblies that might
be used therein.
[0030] FIG. 2 shows a method for fabricating an object. The method
200 is more specifically a generalized method for layer-by-layer
fabrication of an object using sinterable materials.
[0031] As shown in step 202, the method 200 may begin with
providing a material for fabrication. This may include any of a
variety of materials that can be usefully handled in a layer-based
fabrication process such as fused filament fabrication, binder
jetting, stereolithography, and so forth. For example, this may
include sinterable powders of metal, which may be bound together
using a binder system or the like to retain a net shape of an
object during printing and subsequent processing into a final
object. Interface layers of unsinterable materials, or materials
that otherwise resist bonding of an object to an adjacent support
material, may be used to fabricate a separation layer for easily
removable support structures. A number of suitable materials are
described, for example, in U.S. Pat. No. 9,833,839 (incorporated
herein by reference), any of which may be used for the fabrication
of an object, supports and interface layers as contemplated herein.
More generally, any material(s) suitable for use fabricating
objects, supports and interface layers in a layer-based fabrication
system may be employed as the materials in this method 200. It will
further be appreciated that other techniques that are not layer
based, including subtractive techniques such as milling or fluid
jetting, may also or instead be used, and any correspondingly
suitable materials may also or instead be employed as a build
material for fabricating an object.
[0032] Furthermore, additional materials may be employed by a
fabrication system, such as support materials, interface layers,
finishing materials (for exterior surfaces of an object) and so
forth, any of which may be used as a material for fabrication in
the systems and methods contemplated herein.
[0033] As shown in step 204, the method may include fabricating a
layer for an object. This may, for example, include a layer of the
object itself or a layer of a support structure. For a particular
layer (e.g., at a particular z-axis position of a fabrication
system), an interface layer may also or instead be fabricated to
provide a non-sinterable interface or similar release layer or
structure between a support structure (or a substrate such as a
raft, setter, or print bed) and an object. In another aspect,
finishing materials for exterior surfaces may be used, such as
materials that impart desired aesthetic, structural, or functional
properties to surfaces of the object.
[0034] As shown in step 210, a determination may be made whether
the object (and related supports, etc.) is complete. If the object
is not complete, the method 200 may return to step 204 and another
layer may be fabricated. If the object is complete, then the method
200 may proceed to step 212 where post-processing begins.
[0035] As shown in step 212, the method 200 may include shaping the
object. Prior to debinding and sintering, an object is typically in
a softer, more workable state. While this so-called green part is
potentially fragile and subject to fracturing or the like, the more
workable state affords a good opportunity for surface finishing,
e.g., by sanding or otherwise smoothing away striations or other
artifacts of the layer-based fabrication process, as well as spurs,
burrs and other surface defects that deviate from a computerized
model of an intended shape of the object. In this context, shaping
may include manual shaping, or automated shaping using, e.g., a
computerized milling machine, grinding tools, or a variety of
brushes, abrasives and so forth or any other generally subtractive
technique or tool(s). In one aspect, a fluid stream of a gas such
as carbon dioxide may be used to carry dry ice particulates to
smooth or otherwise shape a surface. In this latter approach, the
abrasive (dry ice) can conveniently change phase directly to a gas
under normal conditions, thus mitigating cleanup of abrasives after
shaping the object.
[0036] As shown in step 214, the process 200 may include debinding
the printed object. In general, debinding may remove some or all of
a binder or binder system that retains a build material containing
a metal (or ceramic or other) powder in a net shape that was
imparted by the printer. Numerous debinding techniques, and
corresponding binder systems, are known in the art and may be used
as binders in the build materials contemplated herein. By way of
non-limiting examples, the debinding techniques may include thermal
debinding, chemical debinding, catalytic debinding, supercritical
debinding, evaporation and so forth. In one aspect, injection
molding materials may be used. For example, some injection molding
materials with rheological properties suitable for use in a fused
filament fabrication process are engineered for thermal debinding,
which advantageously permits debinding and sintering to be
performed in a single baking operation, or in two similar baking
operations. In another aspect, many binder systems may be quickly
and usefully removed in a debinding process by microwaving an
object in a microwave oven or otherwise applying energy that
selectively removes binder system from a green part. With a
suitably adapted debinding process, the binder system may include a
single binder, such as a binder that is removable through a pure
thermal debind.
[0037] More generally, the debinding process removes a binder or
binder system from a net shape green object, thus leaving a dense
structure of metal (or ceramic or other) particles, generally
referred to as a brown part, that can be sintered into the final
form. Any materials and techniques suitable for such a process may
also or instead be employed for debinding as contemplated
herein.
[0038] As shown in step 216, the process 200 may include sintering
the printed and debound object into a final form. In general,
sintering may include any process of densifying and forming a solid
mass of material by heating without liquefaction. During a
sintering process, necks form between discrete particles of a
material, and atoms can diffuse across particle boundaries to fuse
into a solid piece. Because sintering can be performed at
temperatures below the melting temperature, this advantageously
permits fabrication with very high melting point materials such as
tungsten and molybdenum.
[0039] Numerous sintering techniques are known in the art, and the
selection of a particular technique may depend upon the build
material used, the size and composition of particles in a material
and the desired structural, functional or aesthetic result for the
fabricated object. For example, in solid-state (non-activated)
sintering, metal powder particles are heated to form connections
(or "necks") where they are in contact. Over a thermal sintering
cycle, these necks can thicken and create a dense part, leaving
small, interstitial voids that can be closed, e.g., by hot
isostatic pressing (HIP) or similar processes. Other techniques may
also or instead be employed. For example, solid state activated
sintering uses a film between powder particles to improve mobility
of atoms between particles and accelerate the formation and
thickening of necks. As another example, liquid phase sintering may
be used, in which a liquid forms around metal particles. This can
improve diffusion and joining between particles, but also may leave
lower-melting phase within the sintered object that impairs
structural integrity.
[0040] It will be understood that debinding and sintering result in
material loss and compaction, and the resulting object may be
significantly smaller than the printed object. However, these
effects are generally linear in the aggregate, and net shape
objects can be usefully scaled up when printing to create a shape
with predictable dimensions after debinding and sintering.
Additionally, as noted above, it should be appreciated that the
method 200 may include sending a fabricated object to a processing
facility such as a service bureau or other remote or outsourced
facility, and the method 200 may also or instead include receiving
the fabricated object at the processing facility and performing any
one or more of the post-fabrication steps described above such as
the shaping of step 212, the debinding of step 214, or the
sintering of step 216.
[0041] FIG. 3 shows a mold lock condition. In general, an object
300 may be three-dimensionally printed using any of a variety of
fabrication techniques such as any of the techniques described
herein. Where necessary or helpful for fabrication, a support 302
may be fabricated adjacent to the object 300 to provide support for
the object 300 during fabrication and/or subsequent handling. An
interface layer 304 may be fabricated between the object 300 and
the support 302 in order to prevent undesired bonding of the object
300 to the support 302, however for certain geometries the support
302 may enclose the object 300 in a manner that does not provide
any path for removal of the object 300 from the support 302.
[0042] In a typical fabrication process, a raft 306 may also be
fabricated as a substrate to receive the object 300 and support 302
during printing, and fabrication may be performed vertically along
a vertical axis 308, often referred to as the z-axis, in a
layer-by-layer fashion to render a physical realization of the
object 300 above the raft 306. Some surfaces 310 of the support 302
may touch the raft 306, i.e., vertically project downward into
contact with the raft 306, and other regions 312 of the support 302
may not touch the raft 306, i.e., vertically project downward into
contact with the object 300 rather than the raft 306. As discussed
below, an automated mold lock remediation process may address these
regions differently.
[0043] Where the object 300 and support 302 are, e.g., sintered or
otherwise thermally processed into substantially solid metal pieces
or the like, removal of the support 302 can impose substantial
post-fabrication processing in order to liberate the object 300
from the support 302, particularly where the geometry of the
support 302 has no linear draw path for separation from the object
300, a condition referred to generally herein as mold lock. While
the three-dimensional model for the support 302 may be modified
prior to fabrication, e.g., in a computer aided design environment
or the like, in order to break the support 302 into a number of
sub-components that can be disassembled from around the object 300
after solidification, this is typically a labor-intensive process
that is often performed manually. As described below, these
challenges may be mitigated by providing automated remediation of
mold lock conditions.
[0044] FIG. 4 shows a flow chart of a method for remediating mold
lock conditions. In general, when supports are generated for a
part, they may undergo a number of preliminary checks and simple
modifications, followed by a systematic, two-dimensional strategy
for detection and remediation of mold lock conditions. If these
efforts fail, then a number of three-dimensional remediation
strategies may be employed, followed by a notification to a user if
mold lock conditions defy automated resolution. In addition to
providing a number of simplified two-dimensional computational
strategies for mold lock remediation, the method 400 described
below may advantageously stage remediation strategies so that more
computationally complex, three-dimensional remediation strategies
are deferred until other strategies have proven unsuccessful.
[0045] As shown in step 402, the method 400 may include receiving a
digital model of an object and a support structure. Receiving the
model may include receiving the model within a computer aided
design environment with a user interface for user interaction, or
receiving the model by a tool or other program or environment
configured to automate mold lock remediation as contemplated
herein. In general, the model may include a model of any object
suitable for fabrication along with support structures to
physically support the object during fabrication. In general,
support structures may be automatically positioned according to
design rules for a particular fabrication process. The design rules
may include fabrication design rules that implicitly or explicitly
specify where support is needed, e.g., to support bridges or
overhangs in an object during printing. The design rules may also
or instead include sintering design rules that similarly specify
where support is needed to prevent deformation or breakage of an
object during sintering.
[0046] As noted above, during fabrication, an interface layer may
be applied between surfaces of the model and the support in order
to prevent coupling of the two surfaces during fabrication. As more
generally described above, the digital model may include a raft, an
object for fabrication on the raft, and a support for fabrication
with the object to provide physical support according to one or
more design rules, as well as an interface layer between any of the
foregoing.
[0047] As shown in step 404, the method 400 may include performing
a number of initial checks on the model to determine whether mold
lock remediation is required. In one aspect, this may include
performing an initial check to determine whether the object can be
separated from the support along a vertical axis. While the current
techniques favor two-dimensional processing for purposes of
computational speed and simplicity, a preliminary check may be
performed on the aggregate, three-dimensional structure of the
object and support to determine whether the object can be simply
removed, e.g., through a straight vertical motion, from the
support, thus obviating further mold lock mitigation.
[0048] In another aspect, this may include a number of simple
geometric attempts to address mold lock. For example, this may
include separating regions of the support touching the raft (and a
volume vertically above and contiguous with such regions) from
regions of the support not touching the raft along a vertical axis
and performing a check to determine whether the object can be
separated from the modified structures of the support along the
vertical axis. In general, this seeks to determine whether mold
lock is being created by horizontal shelves that can be addressed
by simply decoupling regions below the shelf from other regions of
the support structure.
[0049] Once preliminary checks based on, e.g., vertical
three-dimensional draw paths, are complete, the method 400 may
proceed to other mold lock remediation steps as necessary.
[0050] As shown in step 406, the method 400 may include dividing
the model into a number of layers for processing. This may, for
example, include layers formed by planar, horizontal cross sections
through the digital model. In one aspect, the number of layers may
correspond to material deposition layers for an additive
fabrication process. Using the physical deposition layers may
significantly simplify processing where a current,
fabrication-ready model or the like is already realized in a number
of layers such as layers corresponding to stereolithography cross
sections or fused filament fabrication tool paths.
[0051] As shown in step 408, the method 400 may include identifying
draw paths for removing support from the object on a layer by layer
basis within the layers of the digital model. This may include, for
each layer of the digital model created above, identifying one or
more draw paths for separating a layer of support formed by a cross
section of the support from a layer of the object formed by a cross
section of the object within the layer of the digital model. The
draw path, may for example, include a range of angles over which a
first rigid shape of the cross section of the support can be
separated in a straight line from a second rigid shape of the
object, or any other single linear path or range of compound paths
suitable for uncoupling rigid two-dimensional shapes within a
plane. Identifying the one or more draw paths may also or instead
include testing for linear separation in a straight line at a
number of discrete angles over a predetermined range of angles, or
over a continuous range of angles, or any other similar strategy
for systematically testing linear draw paths.
[0052] As shown in step 410, the method 400 may include identifying
locked layers, e.g., layers of support with geometric features that
prevent decoupling from layers of the object within the plane. In
one aspect, this may include identifying one of the number of
layers as a locked layer when the layer of support has no draw path
for separating the layer of support from the layer of the object.
This may also or instead include identifying one of the number of
layers as a locked layer when the layer of support is vertically
coupled to a second layer of the support having no draw path in
common with the layer of support.
[0053] In one aspect, this may include a progressive search
strategy for available draw paths. For example, a layer of support,
or more specifically, the two-dimensional shape of the layer in a
plane, may be checked in eight directions (e.g., two directions
along four axes) for possible movement relative to the
two-dimensional shape of the object in that plane. If a draw path
is identified, other interstitial directions may also be checked,
e.g., at half intervals to the originally checked directions. So,
for example, where four axes are initially checked and a draw path
is identified for one of the axes, the method 400 may include
checking at 22.50-degree angles about the axis of the identified
draw path.
[0054] As shown in step 412, the method 400 may include identifying
locked volumes based on the locked layers. In general, this may
include vertically traversing the layers of object and support to
identify contiguous layers of support that cannot, as a group
vertically separate from the object. In one aspect, this includes
identifying a mold locked region of the support including one of
the locked layers of support identified in step 410, along with any
vertically contiguous support layers that collectively form a
locked volume.
[0055] This may also include traversing upward and/or downward from
a locked layer until a movable layer is identified. The intervening
collection of layers, all of which are collectively locked, may
then be sliced horizontally to separate them from other groups of
layers, and these horizontal slices may, for example, be flagged
for other three-dimensional strategies as discussed herein. In one
aspect, additional steps may be taken to prevent piecemeal,
layerwise processing. For example, where a single layer (or small
number of adjacent layers) is removable, but positioned immediately
adjacent to two locked layers, the removable layer may be
associated with one or both of the locked layers in order to avoid
separately fabricating a single, removable support layer. In this
process, groups of movable layers may also be formed, e.g., so that
a group of adjacent layers share at least one common draw path for
horizontal removal. These groups may be horizontally separated from
one another for independent, horizontal removal.
[0056] As shown in step 413, the method 400 may include dividing
the locked volume of the mold locked region to attempt removal as
smaller, separate pieces. This may, for example, include dividing
the locked volume into one or more subregions with one or more
vertical planes through the locked volume. This may also or instead
include iteratively attempting an increasing number of planar
slices until the one or more subregions can be horizontally removed
or a threshold is reached. While this planar slicing strategy may
be deployed in a deterministic manner (e.g., bisect, and then
bisect again), other strategies may also or instead be employed.
For example, planar slices may be positioned based on information
about the aggregated draw paths for individual layers of the locked
volume. In another aspect, the planar slices may be selected and
arranged to address regularly occurring use cases. For example, two
planes intersecting at or near a centroid of the locked volume will
provide removable support structures for annular or toroidal
shapes, and relieve a number of other polygonal, two-dimensional
locking conditions.
[0057] As shown in step 414, the method 400 may include evaluating
the resulting structure including the subregions of support
structure to determine whether the mold lock condition has been
remediated. This may, for example, include attempting horizontal
removal of the subregions of the support from the object. If the
one or more subregions can be removed (e.g., horizontally removed),
then the method 400 may proceed to step 418 for processing of the
remaining digital model. If the one or more subregions cannot be
removed, then the method 400 may proceed to step 416 for further
processing of the locked volume.
[0058] As shown in step 416, if the one or more subregions cannot
be horizontally removed, the method 400 may include employing one
or more three-dimensional remediation strategies to address the
mold locked region. In one aspect, the three-dimensional
remediation strategies may include vertically moving the mold
locked region after a second mold locked region is removed from a
vertically adjacent volume. That is, when a portion of substrate
such as a raft, or any other volume of support material within the
digital model, is vertically removed, this may expose regions of
support that were previously horizontally enclosed, but can be
removed vertically, such as supports within the center of a
cylinder. In this case, it may be useful to check whether the
separation of a region of support (e.g., using an interface layer
that permits the region to be removed after fabrication) exposes
such support structures for non-vertical movement. Where some
vertical motion is possible but the mold locked region still cannot
be extricated from an object after vertical travel, one or more
horizontal slices through the mold locked region may usefully be
employed to permit the mold locked region to be removed in a series
of horizontal segments that individually travel vertically and then
horizontally out of engagement with the object.
[0059] In another aspect, the three-dimensional remediation
strategies may include subdividing the mold locked region into a
number of volumetric subregions and searching for three-dimensional
draw paths for removing the volumetric subregions from the object.
In this approach, a mold locked region is simply subdivided into
smaller volume pieces in order to attempt removal. The volumetric
subregions may, for example, be sized for removal through an
opening in the object. More generally, any regular or irregular
pattern, such as a vertical and/or a horizontal grid pattern, may
be applied to the mold locked region of support material to attempt
extraction of individual volumetric subregions.
[0060] Other strategies may also or instead be employed. For
example, for internal support structures traversing diagonally
upward through an object, it may be necessary to identify
layer-to-layer overlaps so that sufficient clearance can be added
to the interface layer for travel of the entire support at an
off-vertical angle during removal. In another aspect, features such
as holes or openings to interior spaces may be usefully located and
characterized using a number of three-dimensional processing
techniques, and enclosed support may be subdivided into shapes that
can be removed through such openings. These and other techniques
may be used in any of a variety of combinations to identify and
facilitate removal of support structures within a three-dimensional
object. While some such techniques are known in the art, the method
400 described herein advantageously defers many of these more
computationally complex processing challenges, known or otherwise,
until various two-dimensional techniques have been applied to
existing supports.
[0061] In the event that these and other three-dimensional
remediation strategies fail to achieve a remediation of a mold lock
condition, the method 400 may include providing a notification to a
user of the unremediated mold lock condition. This may include a
notification within a computer aided design application, an
electronic communication sent through other media, or some
combination of these or the like. Regions of unremediated mold lock
may usefully be flagged or visually highlighted within a user
interface to facilitate manual inspection and remediation as
appropriate. After completion of three-dimensional remediation
strategies and any other related processing steps, the method 400
may proceed to step 418 where additional volumes may be
processed.
[0062] As shown in step 418, the method 400 may include processing
a remaining digital model, e.g., a digital model excluding the one
or more subregions of the support that have been unlocked from the
object as described above, for mold lock remediation. Thus, the
remediation steps may be repeated as needed to ensure that all of
the potentially mold locked support structures are addressed prior
to fabrication.
[0063] As shown in step 420, the method 400 may include fabricating
the object and the support from the digital model, as well as the
interface layers positioned between the object and support for
disassembly and removal of the support structure from the object
after fabrication. For volumes of support that have been subdivided
as generally described herein, fabricating may similarly include
fabricating an interface layer between the one or more subregions
of a mold locked region so that the subregions can be disassembled
after fabrication. In another aspect, fabricating the object (and
support) may include generating instructions executable by a
three-dimensional printer to fabricate the object and the support,
including fabricating an interface layer between the object and the
support. This may also or instead include generating instructions
to fabricate a second interface layer between one or more
subregions of a mold locked region, such as any of the subregions
described above. Suitable instructions may be created, e.g., for
any of a number of types of printers including fused filament
fabrication printers, stereolithography printers, binder jet
printers, and so forth.
[0064] FIG. 5 illustrates an object and support that have been
processed to remediate mold lock. In general, an object 502 such as
a ring may be fabricated from a build material. Supports 504, 506,
e.g., for a roof (not shown) to the object 502, may be fabricated
adjacent to the object 502, and separated by an interface layer 508
to prevent bonding between the supports 504, 506 and the object 502
during sintering or other post-processing. By processing on a layer
by layer basis along a vertical axis 510 as described herein, the
outer support 504 may be separated in a number of locations by
additional interface layers 512 to facilitate disassembly and
horizontal removal of the outer support 504 after the object 502
and supports 504, 506 have been sintered into a final part.
[0065] Additionally, after a raft (not shown) below the object 502
has been removed, three-dimensional strategies may be applied to
recognize that the central support 506 can be moved vertically
(downward along the vertical axis 510) for removal from the
interior of the object 502. In this manner, all of the surrounding
supports 504, 506 for the object 502 may be easily removed, e.g.,
by hand, after the object 502 and the supports 504, 506 have been
sintered or otherwise thermally processed into a final part such as
one or more rigid, densified metallic components.
[0066] The above systems, devices, methods, processes, and the like
may be realized in hardware, software, or any combination of these
suitable for a particular application. The hardware may include a
general-purpose computer and/or dedicated computing device. This
includes realization in one or more microprocessors,
microcontrollers, embedded microcontrollers, programmable digital
signal processors or other programmable devices or processing
circuitry, along with internal and/or external memory. This may
also, or instead, include one or more application specific
integrated circuits, programmable gate arrays, programmable array
logic components, or any other device or devices that may be
configured to process electronic signals. It will further be
appreciated that a realization of the processes or devices
described above may include computer-executable code created using
a structured programming language such as C, an object oriented
programming language such as C++, or any other high-level or
low-level programming language (including assembly languages,
hardware description languages, and database programming languages
and technologies) that may be stored, compiled or interpreted to
run on one of the above devices, as well as heterogeneous
combinations of processors, processor architectures, or
combinations of different hardware and software. In another aspect,
the methods may be embodied in systems that perform the steps
thereof, and may be distributed across devices in a number of ways.
At the same time, processing may be distributed across devices such
as the various systems described above, or all of the functionality
may be integrated into a dedicated, standalone device or other
hardware. In another aspect, means for performing the steps
associated with the processes described above may include any of
the hardware and/or software described above. All such permutations
and combinations are intended to fall within the scope of the
present disclosure.
[0067] Embodiments disclosed herein may include computer program
products comprising computer-executable code or computer-usable
code that, when executing on one or more computing devices,
performs any and/or all of the steps thereof. The code may be
stored in a non-transitory fashion in a computer memory, which may
be a memory from which the program executes (such as random-access
memory associated with a processor), or a storage device such as a
disk drive, flash memory or any other optical, electromagnetic,
magnetic, infrared or other device or combination of devices. In
another aspect, any of the systems and methods described above may
be embodied in any suitable transmission or propagation medium
carrying computer-executable code and/or any inputs or outputs from
same.
[0068] It will be appreciated that the devices, systems, and
methods described above are set forth by way of example and not of
limitation. Absent an explicit indication to the contrary, the
disclosed steps may be modified, supplemented, omitted, and/or
re-ordered without departing from the scope of this disclosure.
Numerous variations, additions, omissions, and other modifications
will be apparent to one of ordinary skill in the art. In addition,
the order or presentation of method steps in the description and
drawings above is not intended to require this order of performing
the recited steps unless a particular order is expressly required
or otherwise clear from the context.
[0069] The method steps of the implementations described herein are
intended to include any suitable method of causing such method
steps to be performed, consistent with the patentability of the
following claims, unless a different meaning is expressly provided
or otherwise clear from the context. So, for example, performing
the step of X includes any suitable method for causing another
party such as a remote user, a remote processing resource (e.g., a
server or cloud computer) or a machine to perform the step of X.
Similarly, performing steps X, Y and Z may include any method of
directing or controlling any combination of such other individuals
or resources to perform steps X, Y and Z to obtain the benefit of
such steps. Thus, method steps of the implementations described
herein are intended to include any suitable method of causing one
or more other parties or entities to perform the steps, consistent
with the patentability of the following claims, unless a different
meaning is expressly provided or otherwise clear from the context.
Such parties or entities need not be under the direction or control
of any other party or entity, and need not be located within a
particular jurisdiction.
[0070] It should further be appreciated that the methods above are
provided by way of example. Absent an explicit indication to the
contrary, the disclosed steps may be modified, supplemented,
omitted, and/or re-ordered without departing from the scope of this
disclosure.
[0071] It will be appreciated that the methods and systems
described above are set forth by way of example and not of
limitation. Numerous variations, additions, omissions, and other
modifications will be apparent to one of ordinary skill in the art.
In addition, the order or presentation of method steps in the
description and drawings above is not intended to require this
order of performing the recited steps unless a particular order is
expressly required or otherwise clear from the context. Thus, while
particular embodiments have been shown and described, it will be
apparent to those skilled in the art that various changes and
modifications in form and details may be made therein without
departing from the spirit and scope of this disclosure and are
intended to form a part of the invention as defined by the
following claims, which are to be interpreted in the broadest sense
allowable by law.
* * * * *