Note: Descriptions are shown in the official language in which they were submitted.
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5805P17CA
IMPROVED STEREOLITHOGRAPHY SYSTEM
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a stereolithography system and,
in particular,
to a stereolithography system including a tank coated with a wettable
material.
Description of the Related Art
[0002] PCT Application Publication Number WO 2014/126837 to DiSimone et
al.,
the full disclosure of which is incorporated herein by reference, discloses a
method of
forming a three-dimensional object. The method comprises providing a carrier
and an
optically transparent member having a build surface. The carrier and the build
surface
define a build region therebetween. The build region is filled with a
polymerizable liquid
and the build region is irradiated through the optically transparent member to
form a solid
polymer from the polymerizable liquid while concurrently advancing the carrier
away
from the build surface to form the three-dimensional object from the solid
polymer, while
also concurrently: (i) continuously maintaining a dead zone of polymerizable
liquid in
contact with the build surface, and (ii) continuously maintaining a gradient
of
polymerization zone between the dead zone and the solid polymer and in contact
with
each thereof, the gradient of polymerization zone comprising the polymerizable
liquid in
partially cured form. An apparatus for carrying out the method is also
disclosed.
SUMMARY OF THE INVENTION
[0003] It is an object of the present invention to provide an improved
stereolithography system.
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[0004] There is accordingly provided a stereolithography system
comprising an
emitting device and a tank disposed above the emitting device. The tank has an
optically
transparent bottom wall. There is a linear stage that extends away from the
tank and a
carrier platform is moveable along the linear stage away from the tank. There
is also a
wettable material at the optically transparent bottom wall of the tank within
the tank. The
wettable material may be coated on the optically transparent bottom wall of
the tank or
the wettable material may overlay the optically transparent bottom wall of the
tank. The
wettable material may be a hydrogel. The hydrogel may comprise any one of or a
combination of a polysaccharide which may be GelIan gum, an agar substitute,
collagen,
calcium chloride and sodium alginate. The wettable material may include silica
gel. The
wettable material may include urethane.
BRIEF DESCRIPTIONS OF DRAWINGS
[0005] The invention will be more readily understood from the following
description
of the embodiments thereof given, by way of example only, with reference to
the
accompanying drawings, in which:
[0006] Figure 1 is a perspective view of an improved stereolithography
system;
[0007] Figure 2 is a perspective, sectional view of a resin tray of the
stereolithography system;
[0008] Figure 3 is a simplified schematic showing a gap between a wettable
material
on a bottom wall of the resin tray and a three-dimensional object being formed
by the
stereolithography system;
[0009] Figure 4 is an elevation view of the improved stereolithography
system
showing an object starting to be formed by the stereolithography system;
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[0010] Figure 5 is an elevation view of the improved stereolithography
system
showing an object being formed by the stereolithography system; and
[00111 Figure 6 is an elevation view of the improved stereolithography
system
showing an object formed by the stereolithography system.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0012] Referring to the drawings and first to Figure 1, an improved
stereolithography
system 10 is shown. The stereolithography system 10 comprises a base 12 and a
wall 14
that extends vertically from the base 12. There is a tank 16 mounted on the
wall 14 and an
emitting device 18 is mounted on the base 12. The tank 16 is mounted on the
wall 14
above the emitting device 18. The emitting device may be any suitable light-
emitting
device which may be used to cure a polymerizable resin. There is a linear
stage 20 that
extends vertically away from the tank 16 and a carrier platform 22 is moveable
along the
linear stage 20. The stereolithography system 10, as thus far described, is a
generally
conventional stereolithography system used in a "top down" three-dimensional
printing
technique in which new cross-sections of an object being formed are formed at
a bottom
of the object being formed.
[0013] However, as best shown in Figure 2, the tank 16 of the
stereolithography
system 10 has a novel structure. The tank 16 has a bottom wall 24 which is
optically
transparent and there is a plurality of side walls, for example, side walls
26, 28 and 30
which extend from the bottom wall 24 of the tank 16. There is a wettable
material 32 at
the bottom wall 24 of the tank 16 within the tank 16. The wettable material 32
may be
coated on the bottom wall 24 of the tank 16 or the wettable material 32 may
overlay the
bottom wall 24 of the tank 16. The wettable material 32 may have a thickness
of between
1 millimeter and 4 millimeters. The wettable material 32 may be any material
that is
capable of being wetted, i.e. retaining water. In this example, the wettable
material 32 is
in the form of a membrane and overlays the bottom wall 24 of the tank 16.
However, in
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other examples, the wettable material 32 may be coated or formed on the bottom
wall 24
of the tank 16.
[0014] The wettable material 32 may be a hydrogel, for example, a
hydrogel prepared
by mixing a polysaccharide with water/hydrogen peroxide and plasticizer in
different
proportions. The method of preparation may vary according to the
polysaccharide
employed. The hydrogel may include a mix of two or more polysaccharides to
develop
variations in the mechanical properties of the hydrogel. The polysaccharide
may be a
Gellan gum. The hydrogel may include calcium chloride or sodium alginate for
cross-
linking. The hydrogel may include collagen. The hydrogel may include an agar
substitute
such as PhytagelTM which is composed of glucuronic acid, rhamnose, and
glucose. An
example of a formulation of a hydrogel is a hydrogel comprising PhytagelTM at
about
1.5% by weight, sorbitol at about 35% by weight, distilled water at about
63.5% by
weight and calcium chloride (CaC12) at about 0.01 pph.
[0015] The wettable material 32 may include a silica gel which can be
wetted with a
suitable liquid including, but not limited to, hydrogen peroxide, sorbitol,
glycerin and
water. The wettable material 32 may include a clear urethane. Alternatively,
the wettable
material may be a silica gel membrane or a clear urethane membrane. It will
however be
understood by a person skilled in the art that the wettable material may be
any material
capable of being wetted including a wet piece of transparent paper or other
suitable film
or membrane.
[0016] Referring now to Figure 3, and with reference back to Figure 2,
the wettable
material 32 results in a dead zone or a gap 48 at the interface between the
wettable
material 32 and resin in the tank 16. The gap 48 may be a result of
intermolecular forces
of repulsion between the wettable material 32 and the resin in the tank 16
and/ or the gap
48 may be the result of a layer of water which separates the wettable material
32 and the
resin because the resin and water are immiscible. Figure 3 best shows a gap 48
between
the wettable material 32 at the bottom wall 24 of the tank 16 (not shown in
Figure 3) and
an object 50 being formed from the resin in the tank. The gap 48 allows the
object 50 to
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be formed continuously because the object 50 is not formed directly on the
bottom wall
24 of the tank 16 thereby doing away with the need for the object 50 to be
peeled or
pulled away from the bottom wall 24 of the tank 16. It will be understood by a
person
skilled in the art that the resin is cured or polymerized by irradiation to
form the object
50.
[0017] The wettable material 32 may be affixed to the bottom wall 24 of
the tank 16
by using a mould to cast the wettable material 32 in liquid form over the
bottom wall 24
of the tank 16 then curing the wettable material 32 to affix the wettable
material 32 to the
bottom wall 24 of the tank 16. Alternatively, an adhesive may be used to affix
the
wettable material 32 to the bottom wall 24 of the tank 16. Still
alternatively, in other
examples, the wettable material 32 may be affixed to the bottom wall 24 of the
tank 16 by
applying a vacuum to a hollow interior of the bottom wall 24 of the tank 16
through a
conduit.
[0018] Figure 4 shows the object 50 starting to be formed using the
stereolithography
system 10. The carrier platform 22 is disposed within the tank 16 as the
emitting device
18 emits a substantially continuous blast or emission of light 52 as the
object 50 starts to
be formed on the carrier platform 22. The carrier platform 22 then moves
continuously
and upwardly away from the tank 16 as the emitting device 18 emits the blast
or emission
of light 52 and the object 50 is formed continuously as shown in Figure 5.
This process
continues until the object 50 is fully formed as shown in Figure 6. The gap
48, shown in
Figure 3, between the bottom wall 24 of the tank 16 and resin in the tank 16
allows the
object 50 to be formed continuously because the object 50 is not formed
directly on the
bottom wall 24 of the tank 16, thereby doing away with the need for the object
50 to be
peeled or pulled away from the bottom wall 24 of the tank 16.
[0019] A controller 54 may be used to control the duration and the
intensity of the
blast or emission of light depending on the object being formed or part of the
object being
formed. The object 50 being formed in Figures 4 to 6 has solid parts, for
example solid
part 56, and hollow parts, for example hollow part 58. The controller 54 will
increase the
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duration of the blast or emission of light 52 and lower the intensity of the
blast or
emission of light 52 during the formation of the solid part 56. Conversely,
the controller
54 will decrease the duration of the blast or emission of light 52 and
increase the intensity
of the blast or emission of light 52 during the formation of the hollow part
58. The
duration of the blast or emission of light 52 is increased during the
formation of the solid
part 56 because additional time is required for the resin to cure or
polymerize due to the
larger surface area being cured. The intensity of the blast or emission of
light 52 is
lowered during the formation of the solid part 56 to minimize excess heat
which may dry
the wettable material 32. The duration of the blast or emission of light 52 is
decreased
during the formation of the hollow part 58 because less time is required for
the resin to
cure or polymerize due to the smaller surface area being cured. However, the
intensity of
the blast or emission of light 52 is increased during the formation of the
hollow part 58 to
accelerate the dimensional printing process.
[0020] It will be understood by a person skilled in the art that
although the
stereolithography systems as disclosed herein are used to continuously form an
article
that the stereolithography systems as disclosed herein may be used to form an
article
stepwise.
[0021] It will also be understood by a person skilled in the art that
many of the details
provided above are by way of example only, and are not intended to limit the
scope of the
invention which is to be determined with reference to the following claims.
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