U.S. patent application number 16/270724 was filed with the patent office on 2019-08-08 for systems and methods for an improved peel operation during additive fabrication.
This patent application is currently assigned to Formlabs, Inc.. The applicant listed for this patent is Formlabs, Inc.. Invention is credited to Jason Livingston, Jeffery Morin, Yoav Reches, Caitlin Reyda, Steven Thomas.
Application Number | 20190240968 16/270724 |
Document ID | / |
Family ID | 55301508 |
Filed Date | 2019-08-08 |
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United States Patent
Application |
20190240968 |
Kind Code |
A1 |
Thomas; Steven ; et
al. |
August 8, 2019 |
SYSTEMS AND METHODS FOR AN IMPROVED PEEL OPERATION DURING ADDITIVE
FABRICATION
Abstract
According to some aspects, a method of additive fabrication
wherein a plurality of layers of material are formed is provided.
The method may comprise forming a layer of material in contact with
a container, and subsequent to the forming of the layer of
material, actively bending the container around at least one fixed
point such that the layer of material separates from the container.
According to some aspects, an additive fabrication apparatus
configured to form a plurality of layers of material is provided.
The apparatus may comprise a container, a build platform, one or
more force generators, and at least one controller configured to,
subsequent to formation of a layer of material in contact with the
container, actively bend the container around at least one fixed
point via the one or more force generators, such that the layer of
material separates from the container.
Inventors: |
Thomas; Steven; (Cambridge,
MA) ; Reches; Yoav; (Cambridge, MA) ;
Livingston; Jason; (Somerville, MA) ; Morin;
Jeffery; (Boston, MA) ; Reyda; Caitlin;
(Cambridge, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Formlabs, Inc. |
Somerville |
MA |
US |
|
|
Assignee: |
Formlabs, Inc.
Somerville
MA
|
Family ID: |
55301508 |
Appl. No.: |
16/270724 |
Filed: |
February 8, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14462551 |
Aug 18, 2014 |
10201963 |
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16270724 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B33Y 10/00 20141201;
B33Y 30/00 20141201; B29C 64/379 20170801; B29C 64/135 20170801;
B29K 2833/04 20130101; B29C 64/10 20170801 |
International
Class: |
B33Y 30/00 20060101
B33Y030/00; B29C 64/20 20060101 B29C064/20; B29C 64/135 20060101
B29C064/135; B33Y 10/00 20060101 B33Y010/00; B29C 64/10 20060101
B29C064/10 |
Claims
1. A method of additive fabrication wherein a plurality of layers
of material are formed on a build platform, comprising: forming a
layer of material in contact with a container; and operating,
subsequent to the forming of the layer of material, one or more
force generators coupled to the container to apply a force to a
portion of the container, thereby actively bending the container
around at least one fixed point such that the layer of material
separates from the container.
2. The method of claim 1, wherein bending the container around the
at least one fixed point comprises moving at least a portion of the
container while anchoring the container at the at least one fixed
point.
3. The method of claim 1, wherein the at least one fixed point
includes a first end of the container.
4. The method of claim 3, wherein bending the container comprises
moving a second end of the container away from the build
platform.
5. The method of claim 1, wherein causing the layer of material to
separate from the container comprises separating a first portion of
the layer of material from the container prior to separating a
second portion of the layer of material from the container.
6. The method of claim 5, wherein the at least one fixed point
comprises a first fixed point, and wherein the second portion of
the layer of material is closer to the first fixed point than the
first portion of the layer of material.
7. The method of claim 1, wherein forming the layer of material in
contact with the container is performed with the container having a
first curvature, and wherein bending the container results in the
container having a second curvature, greater than the first
curvature.
8. The method of claim 7, wherein the first curvature is that of a
substantially flat surface.
9. The method of claim 1, further comprising moving the build
platform such that the combined motion of the build platform and
the bending of the container cause the layer of material to
separate from the container.
10. The method of claim 1, wherein bending the container comprises
moving ends of the container, and wherein the at least one fixed
point includes one or more points between the ends of the
container.
11. The method of claim 10, wherein causing the layer of material
to separate from the container comprises separating a first portion
of the layer of material at substantially the same time as a second
portion of the layer of material, the first and second portions of
the layer of material being non-contiguous.
12. The method of claim 1, further comprising moving the build
platform relative to the container during operation of the one or
more force generators.
13. The method of claim 1, wherein the container is formed from an
acrylic plastic.
14. At least one computer readable medium comprising instructions
that, when executed, perform a method of additive fabrication
wherein a plurality of layers of material are formed on a build
platform, the method comprising: forming a layer of material in
contact with a container; and operating, subsequent to the forming
of the layer of material, one or more force generators coupled to
the container to apply a force to a portion of the container,
thereby actively bending the container around at least one fixed
point such that the layer of material separates from the
container.
15. The at least one computer readable medium of claim 14, wherein
bending the container around the at least one fixed point comprises
moving at least a portion of the container while anchoring the
container at the at least one fixed point.
16. The at least one computer readable medium of claim 14, wherein
the at least one fixed point includes a first end of the
container.
17. The at least one computer readable medium of claim 16, wherein
bending the container comprises moving a second end of the
container away from the build platform.
18. The at least one computer readable medium of claim 14, wherein
the method further comprises moving the build platform relative to
the container during operation of the one or more force generators.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 14/462,551, filed Aug. 18, 2014, which is incorporated herein
by reference in its entirety.
FIELD OF INVENTION
[0002] The present invention relates generally to systems and
methods for separating a part from a surface during additive
fabrication, e.g., 3-dimensional printing.
BACKGROUND
[0003] Additive fabrication, e.g., 3-dimensional (3D) printing,
provides techniques for fabricating objects, typically by causing
portions of a building material to solidify at specific locations.
Additive fabrication techniques may include stereolithography,
selective or fused deposition modeling, direct composite
manufacturing, laminated object manufacturing, selective phase area
deposition, multi-phase jet solidification, ballistic particle
manufacturing, particle deposition, laser sintering or combinations
thereof. Many additive fabrication techniques build parts by
forming successive layers, which are typically cross-sections of
the desired object. Typically each layer is formed such that it
adheres to either a previously formed layer or a substrate upon
which the object is built.
[0004] In one approach to additive fabrication, known as
stereolithography, solid objects are created by successively
forming thin layers of a curable polymer resin, typically first
onto a substrate and then one on top of another. Exposure to
actinic radiation cures a thin layer of liquid resin, which causes
it to harden and adhere to previously cured layers or the bottom
surface of the build platform.
SUMMARY
[0005] Systems and methods for separating a part from a surface
during additive fabrication are provided.
[0006] Some embodiments include a method of additive fabrication
wherein a plurality of layers of material are formed on a build
platform, comprising forming a layer of material in contact with a
container, and operating, subsequent to the forming of the layer of
material, one or more force generators coupled to the container to
apply a force to a portion of the container, thereby actively
bending the container around at least one fixed point such that the
layer of material separates from the container.
[0007] Some embodiments provide at least one computer readable
medium comprising instructions that, when executed, perform a
method of additive fabrication wherein a plurality of layers of
material are formed on a build platform, the method comprising
forming a layer of material in contact with a container, and
operating, subsequent to the forming of the layer of material, one
or more force generators coupled to the container to apply a force
to a portion of the container, thereby actively bending the
container around at least one fixed point such that the layer of
material separates from the container.
[0008] The foregoing summary is provided by way of illustration and
is not intended to be limiting.
BRIEF DESCRIPTION OF DRAWINGS
[0009] The accompanying drawings are not intended to be drawn to
scale. For purposes of clarity, not every component may be labeled
in every drawing. In the drawings:
[0010] FIG. 1 provides a schematic view of a stereolithographic
printer, according to some embodiments;
[0011] FIG. 2 provides a schematic view of a stereolithographic
printer having formed a plurality of layers of a part, according to
some embodiments;
[0012] FIG. 3 illustrates a mechanical operation for separating a
part from a surface of a stereolithographic printer, according to
some embodiments;
[0013] FIGS. 4A-B depict a first exemplary additive fabrication
device configured to separate a part from a surface by bending the
surface, according to some embodiments;
[0014] FIGS. 5A-B depict a second exemplary additive fabrication
device configured to separate a part from a surface by bending the
surface, according to some embodiments;
[0015] FIGS. 6A-C depict a stereolithographic printer utilizing a
thin film, according to some embodiments;
[0016] FIGS. 7A-C depict wiping of a thin film in a
stereolithographic printer, according to some embodiments;
[0017] FIG. 8 depicts application of pressure to a
stereolithographic printer utilizing a thin film, according to some
embodiments;
[0018] FIG. 9 illustrates a flow chart of a process suitable for
separating a part from a surface during additive fabrication,
according to some embodiments; and
[0019] FIG. 10 illustrates an example of a computing system
environment on which aspects of the invention may be
implemented.
DETAILED DESCRIPTION
[0020] Systems and methods for separating a part from a surface
during additive fabrication are provided. As discussed above, in
additive fabrication a plurality of layers of material may be
formed on a build platform. In some cases, one or more of the
layers may be formed so as to be in contact with a surface other
than another layer or the build platform. For example,
stereolithographic techniques may form a layer of resin so as to be
in contact with an additional surface such as a container in which
liquid resin is located.
[0021] To illustrate one exemplary additive fabrication technique
in which a part is formed in contact with a surface other than
another layer or the build platform, an inverse stereolithographic
printer is depicted in FIGS. 1 and 2. Exemplary stereolithographic
printer 100 forms a part in a downward facing direction on a build
platform such that layers of the part are formed in contact with a
surface of a container in addition to a previously cured layer or
the build platform. In the example of FIGS. 1 and 2,
stereolithographic printer 100 comprises build platform 4,
container 6, axis 8 and liquid resin 10. A downward facing build
platform 4 opposes the floor of container 6, which is filled with a
photopolymer resin 10. FIG. 1 represents a configuration of
stereolithographic printer 100 prior to formation of any layers of
a part on build platform 4.
[0022] As shown in FIG. 2, a part 12 may be formed layerwise, with
the initial layer attached to the build platform 4. The container's
floor may be transparent to actinic radiation, which can be
targeted at portions of the thin layer of liquid photocurable resin
resting on the floor of the container. Exposure to actinic
radiation cures a thin layer of the liquid resin, which causes it
to harden. The layer 14 is at least partially in contact with both
a previously formed layer and the surface of the container 6 when
it is formed. The top side of the cured resin layer typically bonds
to either the bottom surface of the build platform 4 or with the
previously cured resin layer in addition to the transparent floor
of the container. In order to form additional layers of the part
subsequent to the formation of layer 14, any bonding that occurs
between the transparent floor of the container and the layer must
be broken. For example, one or more portions of the surface (or the
entire surface) of layer 14 may adhere to the container such that
the adhesion must be removed prior to formation of a subsequent
layer.
[0023] Techniques for reducing the strength of this bond may
include inhibiting the curing process or providing a highly smooth
surface on the inside of the container. In many use cases, however,
at least some force must be applied to remove the cured resin layer
from the container floor. For example, a force may be applied by
rotating the container to mechanically separate the container from
the part 12. FIG. 3 depicts exemplary stereolithographic printer
100 separating a part from the container by pivoting the container
6 about a fixed axis 8 on one side of the container, thereby
displacing an end of the container distal to the fixed axis a
distance 18 (which may be any suitable distance). This step
involves a rotation of the container 6 away from the part 12 to
separate layer 16 from the container, which may be followed by a
rotation of the container back towards the part. In addition, the
build platform 4 may move away from the container to create a space
for a new layer of liquid resin to form between the part and the
container. Subsequent to this motion, a new layer of liquid resin
is available for exposure and addition to the part being formed.
Each step of the aforementioned curing and separating processes may
continue until the part is fully created. By progressively
separating the part and the container base, such as in the steps
described above, the peak force and/or total force necessary to
separate the part and container may be minimized.
[0024] However, multiple problems may arise due to the application
of force during the above-described processes. For example, in some
use cases a force may be applied to and/or through the part itself.
A force applied to the part may, in some use cases, cause the part
to separate from the build platform, rather than the container,
which may disrupt the fabrication process. In some use cases, a
force applied to the part may cause deformation or mechanical
failure of the part itself.
[0025] The inventors have recognized and appreciated that the
above-described problems with the separation processes may be
reduced by minimizing forces applied to the part by applying such
forces gradually and/or evenly to the part. While a higher force
may provide fast separation of the part and the container, it may
run a greater risk of deforming the part. A lower force, in
contrast, may produce a more precise printed part with lower risk
of deformation. By applying force gradually to a part, such as by
performing a "peeling" process in which the force gradually
increases over time and/or is maintained at a lower force on the
part for a longer time, the part may be separated from the
container using a minimal amount of force. Alternatively, or
additionally, applying force evenly to a part may minimize the
force applied to each region of the part. For example, force
applied to a part may cause a large force to be applied to a
particular localized region of the part, e.g., due to the geometry
of that region and a smaller force to be applied to the remainder
of the part. This may result in the localized region being deformed
or otherwise negatively impacted by the large force. By instead
applying force evenly to the part, deformation of one or more
regions of the part due to higher localized forces acting in the
regions may be avoided.
[0026] "Separation" of a part from a surface, as used herein,
refers to the removal of adhesive forces connecting the part to the
surface. It may therefore be appreciated that, as used herein, a
part and a surface may be separated via the techniques described
herein, though immediately subsequent to the separation may still
be in contact with one another (e.g., at an edge and/or corner) so
long as they are no longer adhered to one another.
[0027] The inventors have further recognized and appreciated that
performing a peel by bending the container may provide a way to
apply separation forces gradually and/or evenly to a part. Bending
of the surface of the container may naturally minimize forces
applied to the part since a container that is curved relative to
the region of contact between the part and a surface may provide
the gradual and/or even application of force that aids the
minimization of force.
[0028] In some embodiments, performing a peel includes bending a
container. Bending the container may result in a more gradual
and/or even peel, as discussed above, relative to a peel operation
in which the container is, for example, kept rigid and rotated. The
container may be bent in any suitable way, including around any
number of fixed points, such that the part separates from the
container while the fixed points remain in place and such that the
container does not rotate around the fixed points. For example, the
container may be pulled down (e.g., away from the build platform)
while one or more points of the container are fixed, such that a
layer of a part in contact with the container is gradually peeled
from the container. Bending the container may provide a more
gradual peel of a layer with forces more evenly applied to the part
compared to a peel operation that rotates the container (e.g.,
exemplary stereolithographic printer 100 shown in FIG. 3, and
discussed above). In some use cases, the container is bent such
that its curvature increases. For example, in some use cases the
container may be bent from a flat, or substantially flat,
configuration into a convex or concave configuration.
[0029] In some embodiments, one or more fixed points of the
container around which a container is bent are formed by mechanical
fastening and/or by adhering those fixed points such that the
container does not move and/or rotate about those points. For
example, one or more points of a container may be attached to a
frame (e.g., via one or more fasteners, via one or more adhesives
and/or otherwise) so that a force applied to another region of the
container may cause at least part of the container to bend while
the fixed point or points remain in place.
[0030] In some embodiments, bending of a container is achieved
through active means, such as by using one or more force generators
to actively push and/or pull regions of the container. The one or
more force generators may be coupled to any suitable mechanism or
mechanisms such that activation of a force generator causes a force
to be applied to one or more points of the container. In some
embodiments, active bending of the container is performed via one
or more actuators, such as motors (e.g., stepper motors). The one
or more actuators may be controlled by any number of suitable
controllers, including one or more general purpose processors,
Application Specific Integrated Circuits (ASICs),
Field-Programmable Gate Arrays (FPGAs) and/or combinations thereof.
Bending via active means may reduce forces transmitted to the part
compared with passive means, such as by causing the container to
bend via motion of the build platform (i.e., so that the adhesive
forces between the build platform, part and container cause the
container to bend). By using active means to apply a force to a
region of the container that is not close, or adjacent, to a layer
of a part in contact with the container, compressive forces that
might otherwise be applied to the part may be reduced.
[0031] In some embodiments, the build platform may move during a
peel operation in addition to bending of the container. Moving the
build platform may, in some use cases, aid separation of the part
from the container. For example, the build platform may be moved
toward the container while the container is being bent, thereby
further reducing forces applied to one or more regions of the part.
The build platform may be moved simultaneously with the bending of
the container and/or subsequent to bending being completed. Where
the container is bent through active means, as described above,
movement of the build platform may provide an additional mechanism
with which to control forces applied to a part in contact with the
container. For example, separation of a part from a container
performed solely by moving the build platform upwards can only be
adjusted by altering the speed of the build platform. In contrast,
separation performed using active means in addition to the movement
of the build platform may adjust the relative speed and timing of
the two motions, thus providing greater control over the forces
during separation.
[0032] In some embodiments, the container may be rotated during a
peel operation in addition to bending of the container. Rotating
the container may, in some use cases, aid separation of the part
from the container. For example, the container may be rotated away
from the build platform while the container is being bent, thereby
further reducing forces applied to one or more regions of the part.
The container may be rotated simultaneously with the bending of the
container and/or subsequent to bending being completed.
[0033] As discussed above, the container may be bent around one or
more fixed points. In some embodiments, the one or more fixed
points include an end of the container. For example, an end of the
container may be kept substantially fixed while one or more forces
are applied to one or more portions of the container, thereby
causing the container to bend. An end of the container may, for
example, include a point at which a bottom surface of the container
meets a side surface of the container (of which there may be
multiple such points). Motion of the portion or portions of the
container may be in any direction, such as upwards (e.g., towards
the build platform) and/or downwards (e.g., away from the build
platform). In some embodiments, the container is bent around one or
more fixed points in proximity to a part that is in contact with
the container. This may reduce forces applied to the part by
simultaneously peeling two sides of the layer away from the
container.
[0034] In some embodiments, the container comprises a material that
is able to be repeatedly elastically deformed without premature
failure. As discussed above, the container may hold a fabrication
material, such as a liquid photopolymer, and provide a
substantially flat surface on which to form a layer of a part.
Accordingly, the container should generally be sufficiently rigid
to perform these functions. However, in order to bend a sufficient
amount to separate a part from the container, the container may
also have some flexibility. A non-limiting list of exemplary
materials from which the container may be formed include one or
more polymeric materials, such as Polyethylene Terephthalate (PET),
Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE),
Poly(methyl methacrylate) (PMMA), Polydimethylsiloxane (PDMS),
Polyvinyl Chloride (PVC), Polypropylene (PP), and/or any acrylic
plastic. In some embodiments, the inventors have found that
appropriate materials for the container have a stiffness such that
the container deflects a distance between 10-50 mm with an
application of force between 5-25 N. Alternatively, or
additionally, in some embodiments a suitable container may be
capable of substantial deflection with a peak strain of no more
than 5-10%, and preferably less than 5%.
[0035] Subsequent to the part being separated from the container,
the container and/or build platform may move in preparation for a
subsequent layer of the part being formed. This movement may be a
reverse motion of the motion used to separate the part from the
container, though may alternatively be a different motion. In
embodiments in which the container and part both move, any flexure
and/or motion of the container subsequent to the separation of the
container and part may, or may not, be coordinated in the manner
described above for bending the container. For example, it may be
beneficial to move the container and/or part to a new position in
preparation for forming a new layer of the part more rapidly than
the motion used to separation the container from the part, e.g., to
reduce the total time needed to form the part.
[0036] Additional improvements may be readily implemented to reduce
peel speed and/or to limit the maximum and/or overall force
applied. In some embodiments, a force generator may be modified to
apply force in a non-linear fashion, for example through a guide
channel which shapes the direction of the force applied.
Additionally, or alternatively, a force generator may apply a force
at an angle offset from the normal of the container's surface. In
some embodiments, the container may be formed with a non-uniform
bottom container thickness such that the bottom thickness increases
further away from the force generator. Such differential stiffness
may advantageously require a higher force to be applied in order to
deflect the far side of the container (the side furthest from the
force generator). This requirement of a higher force may
effectively maintain adhesion of the far side of the part to the
container as the peel begins at the edge near the force generator.
In some embodiments, the acrylic resin container may be
pre-tensioned such that an initial configuration of the container
is deflected towards the build platform. Such a configuration may
tend to counteract downward forces caused by the weight of the
resin and the downward force of the build platform so that the
container and the platform are parallel during the fabrication
phase. In the absence of such a configuration, the downward force
of the build platform during fabrication could cause the container
to curve and create a non-uniform print thickness.
[0037] In some embodiments, part or the entire floor of the
container is formed from a thin film. Using a flexible, thin film
as at least part of the floor of the container may decrease the
overall force applied to a part being formed by allowing a peeling
edge to propagate inward from most or all of the outer edge of the
contact area between the part and the film, rather than from a
discrete number of sides. The thin film may be configured to behave
like a thin sheet, rather than a flexible beam as described above.
The thin film may be separated from the part via active and/or
passive means. For example, an active means may pull on the thin
film to initiate and/or propagate a peeling edge. Alternatively, or
additionally, a passive means, such as a motion of the build
platform, may be performed to initiate and/or propagate peeling of
the film from the part.
[0038] Following below are more detailed descriptions of various
concepts related to, and embodiments of, systems and methods for
separating a part from a surface during additive fabrication. It
should be appreciated that various aspects described herein may be
implemented in any of numerous ways. Examples of specific
implementations are provided herein for illustrative purposes only.
In addition, the various aspects described in the embodiments below
may be used alone or in any combination, and are not limited to the
combinations explicitly described herein.
[0039] Although the embodiments herein are primarily disclosed with
respect to the Form 1 3D Printer sold by Formlabs, Inc., the
Assignee of the present application, and with respect to
stereolithography, the techniques described herein may be equally
applicable to other systems. In some embodiments, structures
fabricated via one or more additive fabrication techniques as
described herein may be formed from, or may comprise, a plurality
of layers. For example, layer-based additive fabrication techniques
may fabricate an object by formed a series of layers, which may be
detectable through observation of the object, and such layers may
be any size, including any thickness between 10 microns and 500
microns. In some use cases, a layer-based additive fabrication
technique may fabricate an object that includes layers of different
thickness.
[0040] Although particular systems and methods for separating a
part from a surface during additive fabrication have been described
and shown herein, it is envisioned that the functionality of the
various methods, systems, apparatus, objects, and computer readable
media disclosed herein may be applied to any now known or hereafter
devised additive fabrication technique wherein it is desired to
separate a part from a surface during fabrication.
[0041] As discussed above, the inventors have recognized and
appreciated that multiple problems may arise due to the application
of force during the peeling process described above and depicted in
FIG. 3. In particular, as shown in FIG. 3, forces applied to the
part during rotation of the container may be undesirable, as they
may lead to increased part distortion and/or failure.
[0042] FIGS. 4A-B depict an exemplary additive fabrication device
configured to separate a part from a surface by bending the
surface, according to some embodiments. Exemplary inverse
stereolithographic printer 400 includes a flexible container 2
located opposite to build platform 4. The flexible container 2
contains uncured photopolymer resin 10. Attached to the build
platform 4 is a part 12, which in the example of FIG. 4A comprises
a number of layers formed by additive fabrication including a first
layer at which the part is attached to the build platform. A force
generator 28 is affixed to one edge of the container, while the
other end of the container 30 is fixed in place relative to the
build platform. As the flexible container 2 bends downward, a
separation edge or mechanical peel 16 initiates. The flexible
container 2 comprises one or more flexible materials, examples of
which are described above.
[0043] As shown in the example of FIG. 4A, one side of the flexible
container 2 is fixed while the opposing side of the flexible
container is coupled to a force generator 28. A force generated by
force generator 28 may be generated in any suitable way, such as
with a stepper motor. When the force generator is activated, the
flexible nature of the container combined with the fixed end 30
allows the container to deflect or bend, as shown in FIG. 4A,
instead of pivoting as shown in FIG. 3. In the example of FIG. 4A,
as the floor of the flexible container bends downward, the build
platform 4 remains stationary. The bending of container 2 may, in
some use cases, be considered analogous to the bending of a loaded
cantilever beam.
[0044] In the example of FIG. 4A, adhesive forces between the part
12 and the floor of the flexible container 2 may initially resist
the deflection of the container floor. As such, the part 12 may
tend to exert an upward pull on the flexible container 2 through
the adhered cured resin layer 14. The force generator 28, however,
continues to exert a downwards force on the flexible container 2
along one side, thus deflecting the flexible container 2. As the
flexible container 2 is deflected, force exerted on the part 12
through the adhered layer 14 tends to increase. As the force
builds, it eventually becomes great enough to overcome the adhesion
force on the edge of the part 12 proximal to the force generator.
The layer of the part in contact with the container 14 may then
begin to separate or "peel" from the container at a "leading" edge
16. A void created at the leading edge may begin to fill with resin
and the peel propagates across the part 12 until the part 12 is
fully separated from the flexible container 2. Once the part is
separated from the container as shown in FIG. 4B, the build
platform 4 may move upward with the part. The flexible container 2
then returns to a position parallel to the build platform 4 and the
part 12. The upward motion refreshes and replaces the layer of
uncured resin 10 and the next layer of the build can progress. Each
step of the aforementioned curing and peeling processes may then
continue until the part is fully created.
[0045] As discussed above, some embodiments may advantageously
provide for a more gradual separation of a part from a surface than
techniques described above, and/or may advantageously lower the
force needed to perform said separation. With a slower application
of a peel force, a part may separate with lower peak forces and
less distortion overall because the peel is able to progress more
gradually across the part.
[0046] Some embodiments may achieve one or more of the above
advantages by maintaining adhesion between a part and the surface.
For example, as shown in FIGS. 4A-B, a peel may initially propagate
from an edge of the part proximal to a force generator 28. Because
container 2 is flexible, it is partially kept in place by the
upward pull of the forces provided by the adhered layer 14. In
contrast, in the exemplary system of FIG. 3, the separation would
tend to occur globally across the layer since the magnitude of the
attachment force in relation to a force needed to elastically
deform the beam is trivial. Therefore, once the peel is initiated,
a non-flexible container such as that shown in the example of FIG.
3 would continue to separate downward globally in the fixed pivot
motion as shown. In the flexible container system depicted in FIGS.
4A-B, however, because one end of the container is fixed, the beam
will bend and the curvature will be greatest towards the fixed edge
30. Stated otherwise, near the fixed edge the beam will remain flat
for the longest period and thereby facilitate the adherence of
cured resin 14 on the far side of the part 12 to the container
floor while the separation progresses.
[0047] While the overall and maximum separation forces may be
reduced in the example of FIGS. 4A-B, in some use cases the forces
may still be non-uniform across the part 12. This non-uniformity in
the applied force may be undesirable as it may lead to increased
part distortion and/or failure. Since the curvature of the floor of
the container is greatest near the fixed edge 30, the peel may
progress slowest at that edge. Accordingly, areas of the part 12
closer to the force generator 28 may have increased part distortion
and failure.
[0048] FIGS. 5A-B depict an alternate embodiment that addresses
some of the proceeding issues, according to some embodiments. In
the example of FIGS. 5A-B, a flexing force is applied to two or
more sides of the flexible container 2 by two or more force
generators 28 while keeping at least fixed point 31 held in place.
In exemplary inverse stereolithographic printer 500, therefore,
instead of having a fixed side of the container, the container has
opposing forces on two or more sides along with one or more fixed
points between the two sides that work in concert to bend the
container in a concave manner across the container.
[0049] In some use cases, by applying a flexing force from two
directions part peeling may be initiated at multiple locations. For
example, the left and right sides of layer 14 may begin peeling
independently of one another (at the same time, or at different
times), and the final region of the layer to separate from the
container may be located between the left and right sides of the
layer. Once the part 12 and the most recently cured resin layer 14
are separated from the flexible resin container 2, the flexed sides
of the resin container may return to their original position with
the resin container parallel to the part 12 and the build platform
4. As the sides return to the original position, the upward motion
replaces the layer of uncured resin 10 and the next layer of the
build can progress. Each step of the aforementioned curing and
peeling processes may continue until the part is fully created.
Multiple peel sites may, in some use cases, work to reduce overall
force needed, decrease distortion across the part by more evenly
applying forces, and/or reduce peel time.
[0050] It will be appreciated that substantially the same result as
shown in FIGS. 5A-B may equally be effected by keeping one or more
points at the ends of the container fixed and applying a force
between the ends in an upward direction while moving the build
platform upward. As such, exemplary peeling processes that include
bending of a container described here, including but not limited to
those discussed in relation to FIGS. 4A-B and FIGS. 5A-B, may
perform said bending in any suitable way such that the container
bends relative to a part and/or build platform. It will be
appreciated that, in general, such motion may be effected by any
suitable combination of applying force to the container, keeping
one or more points of the container fixed, rotating the container
about an axis and/or moving the build platform, and that the
particular examples discussed herein are simply illustrative of
these techniques.
[0051] FIGS. 6A-C illustrate an exemplary additive fabrication
device configured to separate a part from a surface using a
flexible film, according to some embodiments. Exemplary additive
fabrication device 600 includes a container formed from a thin film
22 and sides 20, which holds resin 10. Thin film 22 may comprise
any highly flexible and/or non-reactive material, such as
Teflon.RTM. (or any other polytetrafluoroethylene-based formula).
The sides of the resin container 20 may be comprised of a more
rigid material such as an acrylic. The film may have any suitable
thickness such that the film is thick enough to maintain structural
integrity through the fabrication process and is thin enough to be
easily removed from the part as described herein. In some
embodiments, the thin film has a thickness between 0.002'' and
0.02''. In some embodiments, the thin film has a thickness equal to
or greater than 0.05'' and less than or equal to 0.01''. Thin film
22 may be fixed to the resin container sides 20 or may be
adjustably tensioned between them. Exemplary additive fabrication
device 600 includes a wiper 24, to be discussed below.
[0052] As shown in FIG. 6A, a layer of cured resin 14 of a part 12
may adhere to the flexible floor of the container 22 during the
fabrication process. As shown in FIG. 6B, the build platform and
part may be lifted upward with adhesion forces causing the film 22
to deform. The flexible film 22 is able to deflect upward with the
part until the necessary separation force is generated by the
upward movement of the part and the downward pull of the container
floor. A mechanical peel 16 then begins at the outer edges of the
part and propagates inward until the part is separated, as shown in
FIG. 6C.
[0053] Using a flexible film layer as part or the entire floor of
the container may decrease the overall force applied to the part by
allowing the peeling edge to propagate inward from the entire outer
edge rather than a discrete number of sides. In the example of
FIGS. 6A-C, the flexibility of the resin container may be such that
the floor of the resin container 22 behaves like a thin sheet,
rather than like a flexible beam. This difference may be typified
by the extent to which the floor of the resin container propagates
beam loading forces across the floor of the container. Flexible
resin containers described above (e.g., as relating to FIGS. 4A-B
and 5A-B) may tend to propagate load across the entire floor of the
container, thus deflecting globally across the layer in contact
with the container. Using a film may result in the load being
concentrated and minimally propagating deflection. With a highly
elastic film layer, the adhesion force may be sufficient to deform
the film layer and ensure the peel progresses gradually across the
part. Further, a film layer 22 may reduce peel discrepancies based
on part placement. Because each part peels independently with a
localized peel, the placement of the part 12 relative to the
container sides 20 may become less relevant.
[0054] In some use cases, the use of a highly flexible film may
result in the weight of resin and force of the build platform and
part to cause unwanted "sagging" deformation in the film. Such
sagging may partially addressed by the use of a wiper. FIGS. 7A-C
depict the use of such a wiper 24 in exemplary container 700 having
thin film 22, ends 20 and comprising resin 10. In the example of
FIGS. 7A-C, the wiper lifts the film up towards the bottom of the
part or build platform and so positions the film prior to each
build layer to ensure a uniform thickness of resin between the
build platform 4 and the resin tank floor 22.
[0055] As shown in the exemplary progression from FIG. 7A to FIG.
7B to FIG. 7C, the wiper may move from one side of the container to
the other while pushing the sag out of the film until it is
sufficiently parallel to the build platform 4 (see FIGS. 6A-C). The
film floor may be held in place by suction forces between the
container floor 22 and the build platform 4 or part 12. This
suction may depend on the viscosity of the resin and/or on the size
of a part currently being fabricated. While the wiper 24 is
depicted as a cylindrical roller in FIG. 7, the wiper may be of any
suitable shape and may progress across the film floor in any
suitable way, such as from one side to the other as shown in FIGS.
7A-C, or in a coordinated pivoting motion like windshield wipers.
Following this motion, a thickness of resin suitable for
fabricating a layer of a part may be left between the film and
either the build platform 4, or after fabrication has commenced,
the part 12. In some embodiments, the wiper may proceed below the
film such that it accelerates smoothly with minimal frictional
forces. Moving the wiper too slowly could allow the film floor 22
to sag again behind the wiper, but moving the wiper too quickly may
cause undesirable friction as the blade accelerates. In some
embodiments, the wiper speed is between 65 mm/s and 75 mm/s.
[0056] In some embodiments, the viscosity of the resin and suction
forces created between the build platform 4 and the floor of the
container 22 are utilized to maintain the correct position of the
film while the next layer is printed. However, in some use cases,
such forces may be insufficient to hold the film in place. In such
use cases, it may be advantageous to apply a further upward force
26 across the floor of the resin container as depicted in FIG. 8 to
ensure the floor of the resin container 22 is parallel to the build
platform when filled with resin and the weight of the part and
build platform. In one embodiment, such force may be provided by
introducing a pressure difference between the lower and upper
(resin contacting) sides of the thin film. The pressure added may
be sufficient to overcome the weight of the resin 10 and the film
floor 22. Such a pressure difference may be provided through any
suitable source, including standard atmospheric pumps, fans and/or
compressed gas. In some embodiments, a pressure difference may be
created by use of a fan placed at the outside of an enclosure
located below the film. In some embodiments, the enclosure may be
sealed to allow higher pressures to build. In some embodiments,
pressure may be created using a standard computer fan, such as a
Rosewill RFX-100 90 mm case fan.
[0057] FIG. 9 illustrates a flow chart of a process suitable for
separating a part from a surface during additive fabrication,
according to some embodiments. Method 900 may be performed by any
suitable additive fabrication apparatus, including but not limited
to a stereolithographic printer as described above, for example in
the exemplary embodiment shown in FIGS. 4A-B and/or FIGS. 5A-B.
[0058] In act 901, a first layer of material is formed via additive
fabrication. The first layer of material may be formed at any time
during additive fabrication of a part. For example, the first layer
may be the sole layer formed (e.g., on a build platform), or may be
the most recently formed layer and may be in contact with one or
more previously formed layers.
[0059] In act 902, the container is bent around one or more fixed
points. As discussed above, motion of any region of the container
may be active or passive. In embodiments in which the container is
bent via active means, the bending may be effected via one or more
force generators, such as actuators. In act 902, bending the
container causes at least the first layer of material to separate
from the container via the peel operation described above, in act
903.
[0060] FIG. 10 illustrates an example of a suitable computing
system environment 1000 on which aspects of the invention may be
implemented. For example, the computing system environment 1000 may
be used to instruct one or more force generators (e.g., actuators)
to apply a force to one or more regions of a container, to move a
build platform, to move a wiper, or any combinations thereof. Such
a computing environment may represent a home computer, a tablet, a
mobile device, a server and/or any another computing device.
[0061] The computing system environment 1000 is only one example of
a suitable computing environment and is not intended to suggest any
limitation as to the scope of use or functionality of the
invention. Neither should the computing environment 1000 be
interpreted as having any dependency or requirement relating to any
one or combination of components illustrated in the exemplary
operating environment 1000.
[0062] Aspects of the invention are operational with numerous other
general purpose or special purpose computing system environments or
configurations. Examples of well-known computing systems,
environments, and/or configurations that may be suitable for use
with the invention include, but are not limited to, personal
computers, server computers, hand-held or laptop devices,
multiprocessor systems, microprocessor-based systems, set top
boxes, programmable consumer electronics, network PCs,
minicomputers, mainframe computers, distributed computing
environments that include any of the above systems or devices, and
the like.
[0063] The computing environment may execute computer-executable
instructions, such as program modules. Generally, program modules
include routines, programs, objects, components, data structures,
etc. that perform particular tasks or implement particular abstract
data types. The invention may also be practiced in distributed
computing environments where tasks are performed by remote
processing devices that are linked through a communications
network. In a distributed computing environment, program modules
may be located in both local and remote computer storage media
including memory storage devices.
[0064] With reference to FIG. 10, an exemplary system for
implementing aspects of the invention includes a general purpose
computing device in the form of a computer 1010. Components of
computer 1010 may include, but are not limited to, a processing
unit 1020, a system memory 1030, and a system bus 1021 that couples
various system components including the system memory to the
processing unit 1020. The system bus 1021 may be any of several
types of bus structures including a memory bus or memory
controller, a peripheral bus, and a local bus using any of a
variety of bus architectures. By way of example, and not
limitation, such architectures include Industry Standard
Architecture (ISA) bus, Micro Channel Architecture (MCA) bus,
Enhanced ISA (EISA) bus, Video Electronics Standards Association
(VESA) local bus, and Peripheral Component Interconnect (PCI) bus
also known as Mezzanine bus.
[0065] Computer 1010 typically includes a variety of computer
readable media. Computer readable media can be any available media
that can be accessed by computer 1010 and includes both volatile
and nonvolatile media, removable and non-removable media. By way of
example, and not limitation, computer readable media may comprise
computer storage media and communication media. Computer storage
media includes both volatile and nonvolatile, removable and
non-removable media implemented in any method or technology for
storage of information such as computer readable instructions, data
structures, program modules or other data. Computer storage media
includes, but is not limited to, RAM, ROM, EEPROM, flash memory or
other memory technology, CD-ROM, digital versatile disks (DVD) or
other optical disk storage, magnetic cassettes, magnetic tape,
magnetic disk storage or other magnetic storage devices, or any
other medium which can be used to store the desired information and
which can accessed by computer 1010. Communication media typically
embodies computer readable instructions, data structures, program
modules or other data in a modulated data signal such as a carrier
wave or other transport mechanism and includes any information
delivery media. The term "modulated data signal" means a signal
that has one or more of its characteristics set or changed in such
a manner as to encode information in the signal. By way of example,
and not limitation, communication media includes wired media such
as a wired network or direct-wired connection, and wireless media
such as acoustic, RF, infrared and other wireless media.
Combinations of the any of the above should also be included within
the scope of computer readable media.
[0066] The system memory 1030 includes computer storage media in
the form of volatile and/or nonvolatile memory such as read only
memory (ROM) 1031 and random access memory (RAM) 1032. A basic
input/output system 1033 (BIOS), containing the basic routines that
help to transfer information between elements within computer 1010,
such as during start-up, is typically stored in ROM 1031. RAM 1032
typically contains data and/or program modules that are immediately
accessible to and/or presently being operated on by processing unit
1020. By way of example, and not limitation, FIG. 10 illustrates
operating system 1034, application programs 1035, other program
modules 1036, and program data 1037.
[0067] The computer 1010 may also include other
removable/non-removable, volatile/nonvolatile computer storage
media. By way of example only, FIG. 10 illustrates a hard disk
drive 1041 that reads from or writes to non-removable, nonvolatile
magnetic media, a magnetic disk drive 1051 that reads from or
writes to a removable, nonvolatile magnetic disk 1052, and an
optical disk drive 1055 that reads from or writes to a removable,
nonvolatile optical disk 1056 such as a CD ROM or other optical
media. Other removable/non-removable, volatile/nonvolatile computer
storage media that can be used in the exemplary operating
environment include, but are not limited to, magnetic tape
cassettes, flash memory cards, digital versatile disks, digital
video tape, solid state RAM, solid state ROM, and the like. The
hard disk drive 1041 is typically connected to the system bus 1021
through an non-removable memory interface such as interface 1040,
and magnetic disk drive 1051 and optical disk drive 1055 are
typically connected to the system bus 1021 by a removable memory
interface, such as interface 1050.
[0068] The drives and their associated computer storage media
discussed above and illustrated in FIG. 10, provide storage of
computer readable instructions, data structures, program modules
and other data for the computer 1010. In FIG. 10, for example, hard
disk drive 1041 is illustrated as storing operating system 1044,
application programs 1045, other program modules 1046, and program
data 1047. Note that these components can either be the same as or
different from operating system 1034, application programs 1035,
other program modules 1036, and program data 1037. Operating system
1044, application programs 1045, other program modules 1046, and
program data 1047 are given different numbers here to illustrate
that, at a minimum, they are different copies. A user may enter
commands and information into the computer 1010 through input
devices such as a keyboard 1062 and pointing device 1061, commonly
referred to as a mouse, trackball or touch pad. Other input devices
(not shown) may include a microphone, joystick, game pad, satellite
dish, scanner, or the like. These and other input devices are often
connected to the processing unit 1020 through a user input
interface 1060 that is coupled to the system bus, but may be
connected by other interface and bus structures, such as a parallel
port, game port or a universal serial bus (USB). A monitor 1091 or
other type of display device is also connected to the system bus
1021 via an interface, such as a video interface 1090. In addition
to the monitor, computers may also include other peripheral output
devices such as speakers 1097 and printer 1096, which may be
connected through a output peripheral interface 1095.
[0069] The computer 1010 may operate in a networked environment
using logical connections to one or more remote computers, such as
a remote computer 1080. The remote computer 1080 may be a personal
computer, a server, a router, a network PC, a peer device or other
common network node, and typically includes many or all of the
elements described above relative to the computer 1010, although
only a memory storage device 1081 has been illustrated in FIG. 10.
The logical connections depicted in FIG. 10 include a local area
network (LAN) 1071 and a wide area network (WAN) 1073, but may also
include other networks. Such networking environments are
commonplace in offices, enterprise-wide computer networks,
intranets and the Internet.
[0070] When used in a LAN networking environment, the computer 1010
is connected to the LAN 1071 through a network interface or adapter
1070. When used in a WAN networking environment, the computer 1010
typically includes a modem 1072 or other means for establishing
communications over the WAN 1073, such as the Internet. The modem
1072, which may be internal or external, may be connected to the
system bus 1021 via the user input interface 1060, or other
appropriate mechanism. In a networked environment, program modules
depicted relative to the computer 1010, or portions thereof, may be
stored in the remote memory storage device. By way of example, and
not limitation, FIG. 10 illustrates remote application programs
1085 as residing on memory device 1081. It will be appreciated that
the network connections shown are exemplary and other means of
establishing a communications link between the computers may be
used.
[0071] The various methods or processes outlined herein may be
implemented in any suitable hardware. Additionally, the various
methods or processes outlined herein may be implemented in a
combination of hardware and of software executable on one or more
processors that employ any one of a variety of operating systems or
platforms. For example, the various methods or processes may
utilize software to instruct a processor to activate one or more
actuators to perform motions such as those described herein, such
as motion of one or more regions of a container and/or of a build
platform. Example of such approaches are described above. However,
any suitable combination of hardware and software may be employed
to realize any of the embodiments discussed herein.
[0072] In this respect, various inventive concepts may be embodied
as at least one non-transitory computer readable storage medium
(e.g., a computer memory, one or more floppy discs, compact discs,
optical discs, magnetic tapes, flash memories, circuit
configurations in Field Programmable Gate Arrays or other
semiconductor devices, etc.) encoded with one or more programs
that, when executed on one or more computers or other processors,
implement the various embodiments of the present invention. The
non-transitory computer-readable medium or media may be
transportable, such that the program or programs stored thereon may
be loaded onto any computer resource to implement various aspects
of the present invention as discussed above.
[0073] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computer or other processor to implement various aspects of
embodiments as discussed above. Additionally, it should be
appreciated that according to one aspect, one or more computer
programs that when executed perform methods of the present
invention need not reside on a single computer or processor, but
may be distributed in a modular fashion among different computers
or processors to implement various aspects of the present
invention.
[0074] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically, the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0075] Various inventive concepts may be embodied as one or more
methods, of which examples have been provided. For example, methods
of separating a part from a surface during additive fabrication
have been provided herein. The acts performed as part of any method
described herein may be ordered in any suitable way. Accordingly,
embodiments may be constructed in which acts are performed in an
order different than illustrated, which may include performing some
acts simultaneously, even though these acts may have been shown as
sequential acts in illustrative embodiments.
[0076] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, definitions in
documents incorporated by reference, and/or ordinary meanings of
the defined terms.
[0077] The indefinite articles "a" and "an," as used herein, unless
clearly indicated to the contrary, should be understood to mean "at
least one."
[0078] As used herein, the phrase "at least one," in reference to a
list of one or more elements, should be understood to mean at least
one element selected from any one or more of the elements in the
list of elements, but not necessarily including at least one of
each and every element specifically listed within the list of
elements and not excluding any combinations of elements in the list
of elements. This definition also allows that elements may
optionally be present other than the elements specifically
identified within the list of elements to which the phrase "at
least one" refers, whether related or unrelated to those elements
specifically identified.
[0079] The phrase "and/or," as used herein, should be understood to
mean "either or both" of the elements so conjoined, i.e., elements
that are conjunctively present in some cases and disjunctively
present in other cases. Multiple elements listed with "and/or"
should be construed in the same fashion, i.e., "one or more" of the
elements so conjoined. Other elements may optionally be present
other than the elements specifically identified by the "and/or"
clause, whether related or unrelated to those elements specifically
identified. Thus, as a non-limiting example, a reference to "A
and/or B", when used in conjunction with open-ended language such
as "comprising" can refer, in one embodiment, to A only (optionally
including elements other than B); in another embodiment, to B only
(optionally including elements other than A); in yet another
embodiment, to both A and B (optionally including other elements);
etc.
[0080] As used herein, "or" should be understood to have the same
meaning as "and/or" as defined above. For example, when separating
items in a list, "or" or "and/or" shall be interpreted as being
inclusive, i.e., the inclusion of at least one, but also including
more than one, of a number or list of elements, and, optionally,
additional unlisted items. Only terms clearly indicated to the
contrary, such as "only one of" or "exactly one of," will refer to
the inclusion of exactly one element of a number or list of
elements. In general, the term "or" as used herein shall only be
interpreted as indicating exclusive alternatives (i.e. "one or the
other but not both") when preceded by terms of exclusivity, such as
"either," "one of," "only one of," or "exactly one of."
[0081] The phraseology and terminology used herein is for the
purpose of description and should not be regarded as limiting. The
use of "including," "comprising," "having," "containing",
"involving", and variations thereof, is meant to encompass the
items listed thereafter and additional items.
[0082] Having described several embodiments of the invention in
detail, various modifications and improvements will readily occur
to those skilled in the art.
[0083] For example, techniques of separating a portion of a part
formed through additive fabrication from a surface were described.
These techniques may be applied in other contexts. For example, any
additive fabrication process in which a portion of a part being
formed becomes in any way attached to a surface other than another
portion of the part or a build platform may utilize techniques as
described herein. Such modifications and improvements are intended
to be within the spirit and scope of the invention. Accordingly,
the foregoing description is by way of example only, and is not
intended as limiting.
* * * * *