U.S. patent application number 16/915624 was filed with the patent office on 2021-12-30 for systems and methods for producing parts at elevated temperatures.
This patent application is currently assigned to Thermwood Corporation. The applicant listed for this patent is Thermwood Corporation. Invention is credited to Kenneth J. SUSNJARA.
Application Number | 20210402655 16/915624 |
Document ID | / |
Family ID | 1000006024461 |
Filed Date | 2021-12-30 |
United States Patent
Application |
20210402655 |
Kind Code |
A1 |
SUSNJARA; Kenneth J. |
December 30, 2021 |
SYSTEMS AND METHODS FOR PRODUCING PARTS AT ELEVATED
TEMPERATURES
Abstract
A mold assembly for producing a part includes a first section, a
second section movably coupled to the first section, and a cavity
defined by the first section and the second section, the cavity
being shaped to receive a part while the first section and the
second section are movably coupled to each other. The mold assembly
includes a joint formed by adjacent surfaces of the first section
and the second section and a seal extending along the joint.
Inventors: |
SUSNJARA; Kenneth J.; (Dale,
IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Thermwood Corporation |
Dale |
IN |
US |
|
|
Assignee: |
Thermwood Corporation
Dale
IN
|
Family ID: |
1000006024461 |
Appl. No.: |
16/915624 |
Filed: |
June 29, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 43/02 20130101;
B29C 43/3607 20130101; B33Y 10/00 20141201; B29C 64/10 20170801;
B29C 35/02 20130101; B33Y 80/00 20141201; B29K 2101/12
20130101 |
International
Class: |
B29C 43/36 20060101
B29C043/36; B29C 43/02 20060101 B29C043/02; B33Y 10/00 20060101
B33Y010/00; B29C 64/10 20060101 B29C064/10; B29C 35/02 20060101
B29C035/02; B33Y 80/00 20060101 B33Y080/00 |
Claims
1. A mold assembly for producing a part, the mold assembly
comprising: a first section; a second section movably coupled to
the first section such that the second section is configured to
move away from the first section during expansion of the part; a
cavity defined by the first section and the second section, the
cavity being shaped to receive a part while the first section and
the second section are movably coupled to each other; a joint
formed by adjacent surfaces of the first section and the second
section; a seal extending along the joint and spaced away from the
cavity, the seal being breakable after the second section has moved
away from the first section; and a separation device that includes
a scissor mechanism including a pair of legs configured to increase
a distance between the first section and the second section.
2. The mold assembly of claim 1, wherein the joint includes a seam
extending between the first section and the second section and the
seal includes a sealing material applied along the seam.
3. The mold assembly of claim 1, wherein the separation device is
configured to apply a force to linearly separate the first section
and the second section.
4.-8. (canceled)
9. A mold assembly, comprising: a first section; a second section
coupled to the first section; a space between the first section and
the second section to receive a part; and a sealing material
applied to a seam between the first section and the second section
at a location separated from the space that receives the part by a
distance, the seam extending from edges of the first and second
sections at a bottom of the space, the sealing material being
configured to: maintain a seal for a part placed in the space when
the first section and second section abut each other, and release
the seal when the first section and the second section are spaced
apart from each other.
10. The mold assembly of claim 9, wherein the sealing material is
formed of a frangible material applied to the seam of the mold
assembly, wherein the distance is defined by a thickness of the
seam.
11. The mold assembly of claim 9, wherein the first section and
second section are movable with respect to each other so as to
enlarge the space.
12. The mold assembly of claim 9, wherein the first section
includes a first surface that forms a first boundary of the space
and the second section includes a second surface that forms a
second boundary, wherein the first and second boundaries are
configured to move away from each other when the first section and
the second section are spaced apart so as to no longer abut each
other.
13.-20. (canceled)
21. The mold assembly of claim 1, wherein the scissor mechanism
includes a rod configured to increase the distance between the
first section and the section sliding within a slide mechanism
connected to a leg of the pair of legs.
22. The mold assembly of claim 1, wherein the seal is formed with a
frangible material that extends to a bottom edge formed by a seam
of the joint.
23. The mold assembly of claim 22, wherein the seam extends from
the cavity to the bottom edge formed by the seam.
24. The mold assembly of claim 1, wherein the pair of legs are
configured to apply a force to linearly separate the first section
and the second section.
25. (canceled)
26. A mold assembly for producing a part, the mold comprising: a
first section; a second section movably coupled to the first
section; a cavity defined by the first section and the second
section, the cavity being shaped to receive a part while the first
section and the second section are movably coupled to each other; a
joint formed by adjacent surfaces of the first section and the
second section; a seal extending along the joint; and a scissor
mechanism having a pair of legs, a slide mechanism and a rod
extending through the slide mechanism and being secured to one leg
of the pair of legs, the scissor mechanism being configured to move
the first and second sections away from each other.
27. The mold assembly of claim 26, wherein the slide mechanism is
configured to permit sliding movement of the rod through the slide
mechanism as the rod expands.
28. The mold assembly of claim 27, wherein the slide mechanism is
configured to restrict sliding movement of the rod through the
slide mechanism as the rod contracts.
29. The mold assembly of claim 1, wherein the scissor mechanism
includes a sliding rod extending across the pair of legs.
30. The mold assembly of claim 29, wherein the sliding rod extends
through a slide mechanism.
31. The mold assembly of claim 30, wherein the sliding rod is fixed
to a leg of the pair of legs.
32. The mold assembly of claim 1, wherein the pair of legs forms a
first pair of ends connected to the first section and to the second
section, respectively, and a second pair of ends that extend away
from the first section and the second section.
33. The mold assembly of claim 9, wherein the seam extends linearly
downwardly from the space to downward-facing surfaces of the first
section and the second section.
34. The mold assembly of claim 33, wherein the sealing material is
disposed below the space and above a separation configured to
modify a distance between the first section and the second section.
Description
TECHNICAL FIELD
[0001] Aspects of the present disclosure relate to apparatus and
methods for fabricating components. In some instances, aspects of
the present disclosure relate to apparatus and methods for
fabricating components (such as, e.g., automobile parts, medical
devices, machine components, consumer products, etc.) via additive
manufacturing techniques or processes, which may be referred to as
3D printing manufacturing techniques or processes.
BACKGROUND
[0002] Additive manufacturing techniques and processes generally
involve the buildup of one or more materials to make a net or near
net shape (NNS) object, in contrast to subtractive manufacturing
methods. Though "additive manufacturing" is an industry standard
term (ASTM F2792), additive manufacturing encompasses various
manufacturing and prototyping techniques known under a variety of
names, including e.g., freeform fabrication, 3D printing, rapid
prototyping/tooling, etc. Additive manufacturing techniques may be
used to fabricate simple or complex components from a wide variety
of materials. For example, a freestanding object can be fabricated
from a computer-aided design (CAD) model.
[0003] A particular type of additive manufacturing is commonly
known as 3D printing. One such process commonly referred to as
Fused Deposition Modeling (FDM) comprises a process of melting a
relatively thin layer of thermoplastic material, and applying this
material in layers to produce a final part. This is commonly
accomplished by passing a continuous thin filament of thermoplastic
material through a heated nozzle, which melts and applies the
material to the structure being printed. The heated material may be
applied to the existing structure in thin layers, melting and
fusing with the existing material to produce a solid finished
product.
[0004] The filament used in the aforementioned process is generally
produced using a plastic extruder, which is comprised of a
specially designed steel screw configured to rotate inside a heated
steel barrel. Thermoplastic material, in the form of small pellets,
is introduced into one end of the rotating screw. Friction from the
rotating screw, combined with heat from the barrel, softens the
plastic, which is then forced under pressure through a small round
opening in a die attached to the front of the extruder barrel. This
extrudes a string of material which is cooled and coiled up for use
in the 3D printer.
[0005] Melting a thin filament of material in order to 3D print an
item may be a slow process, which may be suitable for producing
relatively small items or a limited number of items. The melted
filament approach to 3D printing may be too slow to manufacture
large items. However, the fundamental process of 3D printing using
molten thermoplastic materials may offer advantages for the
manufacture of large parts or a large number of items.
[0006] In some instances, 3D printing a part may involve a two-step
process. In some aspects, 3D printing may utilize a large print
bead to achieve an accurate final size and shape. This two-step
process, commonly referred to as near-net-shape, may begin by
printing a part to a size slightly larger than needed, then
machining, milling or routing the part to the final size and shape.
The additional time required to trim the part to a final size may
be compensated for by the faster printing process.
[0007] Print heads of additive manufacturing machines used to print
thermoplastic material in relatively large beads generally include
a vertically-mounted extruder and a print nozzle to direct round
print bead downward onto a surface and/or part being printed. In
some cases, the flowable material, such as, e.g., molten
thermoplastic material, may be infused with a reinforcing material
(e.g., strands of fiber) to enhance the material's strength. The
flowable material, while hot and pliable, may be deposited upon a
substrate (e.g., a mold), and then pressed down or otherwise
flattened, and/or leveled to a consistent thickness. These
traditional print heads may include an oscillating plate
surrounding the nozzle, the plate being configured to oscillate
vertically to flatten the bead of material against the previous
layer of material. Print heads may also include a roller mechanism,
which may be more efficient for joining layers and squeezing air
from between the layers. The deposition process may be repeated so
that each successive layer of flowable material is deposited upon
an existing layer to build up and manufacture a desired structure
for a component or part. In order to achieve proper bonding between
printed layers, it may be necessary to ensure the temperature of
the previously-deposited layer is within a certain range. For
example, the previously-deposited layer may need to have cooled by
an appropriate amount and thereby solidified sufficiently to
support the weight of the new layer. However, this
previously-deposited layer may also be sufficiently warm to soften
and fuse with the new layer, thus producing a solid part such as a
mold.
[0008] Additive manufacturing, using reinforced thermoplastic
composite material, may be desirable for the production of
relatively large open molds, including molds suitable for
production of thermoset components. Parts, such as thermoset parts,
may be produced with the use of a heated autoclave. Manufacturing
with the use of heated autoclaves may involve a process that makes
use of a mold having a mold cavity that represents the size and
shape of the component desired. Such molds may be produced using
additive manufacturing, for example by depositing a reinforced
polymer material that is able to withstand autoclave temperatures
(e.g., thermal processing temperatures), without distorting or
softening. A thermoset material for forming the part, such as
epoxy, may be provided in the form of a fiber mat infused with
liquid thermoset material. This thermoset (or other suitable
material) may be placed or laid in the mold cavity. The mold cavity
with the thermoset material therein may then be covered with a
sheet of flexible polymer, such as polyethylene, which is sealed
around the exterior of the mold cavity. Additional materials may be
added between the sealed polymer sheet and the thermoset material
to facilitate evacuation of air trapped between the sealed polymer
sheet and the mold cavity surface. At this point, a vacuum may be
applied to the area between the mold cavity surface and the seated
polymer sheet. This vacuum may evacuate the air between the polymer
sheet and the mold cavity surface. As air is evacuated (e.g., from
the mold cavity), ambient air pressure may tend to force the sealed
polymer sheet tightly against the surface of the mold cavity,
compressing the thermoset material between the polymer sheet and
the mold cavity surface tightly against the mold cavity
surface.
[0009] The amount of force generated by this process (e.g., force
acting to compress the thermoset material), may be dependent on the
ambient air pressure surrounding the mold. Accordingly, when
conducting molding processes inside an autoclave, the ambient
pressure may be raised significantly by sealing and pressurizing
the autoclave. Therefore, the force compressing the thermoset
material may be controllably increased, which may result in a
finished component that is relatively strong and dense.
[0010] In some aspects, vacuum may be applied to an interior of the
mold at a period of time that at least partially overlaps a period
of time during which positive pressure is applied to an interior of
the autoclave. Accordingly, it may be desirable to ensure that the
mold is free of pores and configured to sustain vacuum, without any
air leaks, even at the relatively high pressures generated in the
autoclave.
[0011] The above-described molding process may generally involve
relatively slowly heating pressured air inside the autoclave to a
temperature at which the thermoset material undergoes a chemical
reaction, for example, converting from a highly viscous liquid to a
solid. This heating process, which may occur over a relatively long
period of time, may also heat the thermoplastic mold. The
thermoplastic mold may expand as it is heated and contract as it
cools.
[0012] This expansion and contraction of the mold and the part may
be associated with several problems. For example, the mold may tend
to expand to its maximum size before the thermoset material fully
hardens or cures (e.g., chemically converts from a liquid to a
solid). Therefore, it may be desirable to ensure that the
dimensions of the mold are sized such that, when the mold reaches
its maximum expansion, the mold has a desired size and shape. This
may be desirable, for example, because the size and shape of the
expanded mold may determine the dimensions of the produced part.
Accordingly, it may be desirable to machine the mold at room
temperature to a size somewhat smaller than required for the
finished part. As the molded part cools it also tends to contract
at a rate that is significantly less a contraction rate associated
with the mold. It may be desirable to take this contraction into
account when determining the dimensions of the mold at room
temperature.
[0013] Due to the tendency of the mold to contract at a rate
greater than the contraction rate of the molded part, which may be
completely rigid after molding, can create additional problems. For
example, some part shapes or geometries may tend to cause the part
to be compressed and/or squeezed out of a cavity, for example, as
the mold contracts faster than the part. Other part shapes or
geometries may tend to trap the part in the mold such that, if the
mold contracts faster than the trapped part, large forces may be
generated between the part and the mold. These forces may be
sufficiently large to crush the molded part, crack the mold, or
both.
[0014] In order to address these potential issues, some approaches
involve constructing the mold from the same material as the part so
that both expand and contract at the same rate. This approach is
generally significantly more expensive than producing the mold
using additive manufacturing. Therefore, it is desirable to develop
a method by which 3D printed thermoplastic molds could be used to
produce such parts, such methods allowing the use of parts and
molds formed of different materials.
SUMMARY
[0015] Aspects of the present disclosure relate to, among other
things, methods and apparatus for fabricating components via
additive manufacturing or 3D printing techniques. Each of the
aspects disclosed herein may include one or more of the features
described in connection with any of the other disclosed aspects. An
object of this disclosure is an approach that uses a large scale 3D
printing process to produce a mold, which may be sealed with the
use of a frangible sealing material, in such a way that as the mold
and part contracting forces developed cause the mold to fracture or
separate in a controlled manner.
[0016] There are several ways to achieve such fracture and
separation, including methods in which the mold is constructed in
two or more sections or pieces. The mold pieces may be positioned
tightly against each other to form a seam between the pieces. This
seam may be sealed with a material that is sufficient to prevent
air leaking through the joint so that the required vacuum can be
established and maintained.
[0017] In some instances, the sealing material may be configured to
hold the mold pieces together during the heating and curing cycle
but may stretch and/or fracture as the assembly cools and shrinking
forces develop. As an alternative, the mold pieces may be held
together mechanically using springs or other flexible means which
allow the mold pieces to separate upon generation of sufficient
force. This approach may involve the use of material for sealing
the joints so that the required vacuum may be generated and
maintained during the heating and curing process.
[0018] In at least some embodiments, the molded thermoset part may
have insufficient structural strength to generate a force
sufficient to separate or fracture the sealed mold before
sustaining damage to itself. In these instances, it may be
beneficial to mechanically fracture a frangible seal material
holding the mold together. There are various methods of
accomplishing this using an externally generated force, such as a
hydraulic cylinder or mechanical screw mechanism.
[0019] In at least some embodiments, a mechanism may experience
expansion and contraction as it heats and cools, the expansion and
contraction configured to create forces sufficient to fracture the
seal material during cooling without the need for external
control.
[0020] In one aspect, a mold assembly for producing a part may
include a first section, a second section movably coupled to the
first section, and a cavity defined by the first section and the
second section, the cavity being shaped to receive a part while the
first section and the second section are movably coupled to each
other. The mold assembly may also include a joint formed by
adjacent surfaces of the first section and the second section and a
seal extending along the joint.
[0021] In another aspect, a mold assembly may include a first
section, a second section coupled to the first section, and a space
between the first section and second section to receive a part. The
mold assembly may also include a sealing material applied to a seam
between the first section and the second section. The sealing
material may be configured to maintain a seal for a part placed in
the space when the first section and second section abut each other
and release the seal when the first section and the second section
are spaced apart from each other.
[0022] In yet another aspect, a method for molding a part with a
mold assembly may include connecting a first mold section to a
second mold section, applying a sealing material to the first mold
section and the second mold section, and placing a part within a
part-receiving cavity formed by the first mold section and the
second mold section. The method may also include heating the part
within the part-receiving cavity during a curing process, the
heating causing the part-receiving cavity to enlarge due to thermal
expansion of at least one of the part or the mold and maintaining a
seal during at least a portion of the curing process with a sealing
material applied to the first mold section and to the second mold
section.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate exemplary
aspects of the present disclosure and together with the
description, serve to explain the principles of the disclosure.
[0024] FIG. 1 is a perspective view of an exemplary CNC machine or
additive manufacturing apparatus for use with an additive
manufacturing process for forming articles, according to an aspect
of the present disclosure;
[0025] FIG. 2 is a perspective view of an exemplary carrier and
extruder assembly of the exemplary additive manufacturing apparatus
shown in FIG. 1;
[0026] FIG. 3 is an enlarged perspective view of an exemplary
carrier and applicator head assembly of the exemplary additive
manufacturing apparatus shown in FIG. 1;
[0027] FIG. 4 is an enlarged cross-sectional view of the applicator
head assembly shown in FIG. 3;
[0028] FIG. 5 is a perspective view of an exemplary mold assembly
with a part lifting off the mold as the mold contracts;
[0029] FIG. 6 is a perspective view of an exemplary mold assembly
with a part being crushed in the mold as the mold contracts;
[0030] FIG. 7 is a perspective view of an exemplary mold assembly
formed with separate sections employing seal stretching to allow
the mold to conform to the size of a part;
[0031] FIG. 8 is a perspective view of an exemplary mold assembly
formed with separate sections and resilient members to allow the
mold to conform to the size of a part;
[0032] FIG. 9 is a perspective view of an exemplary mold assembly
formed with separate sections and hydraulic cylinders to allow the
mold to conform to the size of a part; and
[0033] FIG. 10 is a perspective view of an exemplary mold assembly
formed with separate sections and a scissor mechanism to allow the
mold to conform to the size of a part.
DETAILED DESCRIPTION
[0034] The present disclosure is drawn to, among other things,
methods and apparatus for fabricating multiple components via
additive manufacturing or 3D printing techniques. Specifically, the
methods and apparatus described herein may comprise an approach
that employs a large-scale 3D-printing process to produce a mold,
with the use of a sealing material, in such a way that as the mold
and part contracting forces developed cause the mold to fracture or
separate in a controlled manner.
[0035] Referring to FIG. 1, an additive manufacturing apparatus,
such as CNC machine 1, may include a bed 20 having a pair of
transversely spaced side walls 21 and 22, a printing gantry 23, a
trimming gantry 36, a carriage 24 mounted on printing gantry 23, a
carrier 25 mounted on carriage 24, an extruder 61, and an
applicator assembly 43 mounted on carrier 25. Printing gantry 23
and trimming gantry 36 may be supported on side walls 21 and 22. A
horizontal worktable 27 having a support surface disposed in an x-y
plane may be supported on bed 20 between side walls 21 and 22.
Printing gantry 23 and trimming gantry 36 may be disposed so as to
extend along a y-axis, supported at respective ends thereof on end
walls 21 and 22. Printing gantry 23 and trimming gantry 36 may be
movable with respect to an x-axis on a set of shared, approximately
parallel guide rails 28 and 29 provided on the upper ends of side
walls 21 and 22. Printing gantry 23 and trimming gantry 36 may each
be displaceable by one or more (e.g., a set of) servomotors mounted
on the printing gantry 23 and trimming gantry 36, respectively. For
example, printing gantry 23 and trimming gantry 36 may be
operatively connected to tracks provided on the side walls 21 and
22 of the bed 20. Carriage 24 may be supported on printing gantry
23 and provided with a support member 30 mounted on and
displaceable along one or more guide rails 31, 32, and 33 provided
on the printing gantry 23. Carriage 24 may be displaceable along a
y-axis on along or more guide rails 31, 32, and 33 via a servomotor
mounted on the printing gantry 23 and operatively connected to
support member 30. Carrier 25 may be mounted on a set of spaced,
vertically-disposed guide rails 34 and 35 supported on carriage 24
for displacement of the carrier 25 relative to carriage 24 along a
z-axis. Carrier 25 may be displaceable along the z-axis by a
servomotor mounted on the carriage 24 and operatively connected to
the carrier 25.
[0036] As best shown in FIG. 2, extruder 61 may be mounted, in a
linearly-movable manner, to carrier 25. For example, extruder 61
may be movably mounted on a set of rails 34 and 35 (FIG. 1) via
suitable bearings. A servomotor 38 may drive an extruder screw of
extruder 61 through a gearbox 39 attached to transition housing 37.
Extruder 61 may receive thermoplastic pellets at the feed housing
40 so that the extruder screw transfers the thermoplastic material
down through the barrel 42 where it is melted by the friction of
the screw and heaters 41. This melted thermoplastic material may
flow, via extruder 61, to a positive displacement melt pump or gear
pump 62 (FIG. 3).
[0037] As best shown in FIG. 3, gear pump 62 may be securely
mounted to the bottom of carrier 25. Gear pump 62 may be driven by
a servomotor 63 through a gearbox 64, and may receive molten
plastic (e.g., thermoplastic material) from extruder 61 (FIG. 2),
and meter precise amounts of thermoplastic material at
predetermined flow rates to nozzle 51 to print the part (e.g., a
mold 80 as described below). An applicator head 43 may be attached
at a position below gear pump 62. Applicator head 43 may include a
bead shaping roller 59, rotationally mounted in carrier bracket 47.
Roller 59 may provide a means for flattening and leveling an
oversized bead of fluid material (e.g., molten thermoplastic)
extruded out of nozzle 51. Carrier bracket 47 may be adapted to be
rotationally displaced by means of a servomotor 60, through a
pulley or sprocket 56 and belt or chain 65 arrangement.
[0038] With reference to FIG. 4, applicator head 43 may include a
housing 46 with rotary union mounted therein. Pulley or sprocket 56
may be machined into the inner hub 76 of the rotary union. An inner
hub 76 may have an opening with a sufficiently large diameter to
allow the heated print nozzle 51 to pass therethrough. Inner hub 76
may rotate on a set of bearings 49 contained within outer housing
75 of the rotary union. The compression roller assembly may be
attached to the inner hub 76 of the rotary union so that the
compression roller 59 rotates about the print nozzle 51. The rotary
union may also contain barb fittings 67 and 68 ported into coolant
passages 70 that encompass or surround the inner hub 76 and the
inside of the outer housing 75 of the rotary union. The coolant
passages 70 may extend to quick disconnect fittings 72 in fluid
communication with an axle 73 of compression roller 59.
[0039] As best shown in FIGS. 2-4, an oversized molten bead of
flowable material (e.g., molten thermoplastic) may be provided
under pressure from a source disposed on carrier 25 (e.g., gear
pump 62) or another source. The bead of flowable material may be
provided to applicator head 43. Thus, gear pump 62, (or another
source of flowable material), may be securely connected to, and in
communication with, nozzle 51. In use, the flowable material 53
(e.g., thermoplastic material) may be heated sufficiently to form a
large molten bead of material, which may be extruded through
applicator nozzle 51 to form large, uniform, and smooth rows of
deposited material on surface 27. Such beads of molten material may
be flattened, leveled, and/or fused to adjoining layers with
substantially no trapped air by bead-shaping compression roller 59
with the layers forming 3D printed products, including relatively
large open molds (e.g., mold 80 described below).
[0040] In some aspects, additive manufacturing systems, including
the above-described additive manufacturing apparatus, may be
configured to produce relatively large open molds. These molds may
be used, for example, in the production of thermoset components. In
particular, molds formed by additive manufacturing may be useful
for providing molds formed with a different material than the part
intended to be produced with the mold. Such molds may be shaped
such that the geometry of the part may tend to force the part away
from the mold cavity or trap the part within the mold cavity (which
may tend to either crush the molded part or crack the mold). For
example, when mold 80 is not made of the same material as the part
81, the part 81 may tend to lift off the mold 80, as shown in FIG.
5, due to mold 80 shrinking faster, and/or to a greater extent, as
compared to part 81. As shown in FIG. 6, depending on the
particular shape of mold 80, part 81 may tend to become trapped in
mold 80, and may eventually crush part 81 or crack the mold 80 due
to the mold 80 shrinking faster, and/or to a greater extent, as
compared to part 81.
[0041] FIGS. 7-10 illustrate exemplary mold assemblies including
molds 80 according to aspects of the present disclosure. Mold 80
may be formed, for example, of a thermoplastic material deposited
by the additive manufacturing apparatus described above with
respect to FIGS. 1-4. Mold 80 may be a relatively large open mold
forming an open space or cavity 78. A pair of laterally-extending
walls of mold 80 may define cavity 78 and define opposing first and
second boundaries of cavity 78. These walls may surround part 81
when the part 81 is inserted into cavity 78 (e.g., in a vertically
downward direction). As cavity 78 may form an open cavity, for
example a cavity open in an upward direction, a sheet of material
(not shown) may be placed around cavity 78 to form a seal around
cavity 78 to facilitate a molding process with an autoclave, for
example.
[0042] In some aspects, as shown in FIG. 7, thermoplastic mold 80
may be constructed as a plurality of sections 90. Mold 80 may be
connected with a sealing material 83, such that contracting forces
of mold 80 and part 81 may cause one or more components of mold 80
to fracture or separate in a controlled manner. In order to
facilitate separation of mold 80, mold 80 may be constructed in two
or more pieces or sections 90. However, mold 80 may be formed of a
different number of sections, including three sections 90, four
sections 90, or more. In at least some configurations, sections 90
of mold 80 may be positioned tightly against each other while seam
82 may extend between each section 82. Seam 82 may be sealed with a
material 83, such as vulcanized silicone of a formulation that can
withstand curing temperatures, sufficient to prevent air
transmission or leaks through the joint formed at seam 82 so that
vacuum may be established and maintained (e.g., during a vacuum
molding process). In some aspects, seam 82 may include a pair of
opposing surface of sections 90 that may be brought into contact
with each other. Sealing material 83 may extend along a joint
between each pair of sections 90, and may oppose cavity 78. For
example, when cavity 78 forms an upward-facing cavity, sealing
material 83 may extend along a bottom surface of mold 80 formed by
an intersection of a plurality (e.g., a pair) of abutting mold
sections 90. Therefore, when a sealing sheet is placed to seal
cavity 78, sealing material 83 may maintain the seal and facilitate
the application of vacuum to remove air between the polymer sheet
and the surface of mold 80.
[0043] In some configurations, sealing material 83 may hold
sections 90 of mold 80 together during heating and curing cycles
(e.g., while mold 80 is placed in an autoclave), but may be
configured to stretch and/or fracture as the assembly cools and
shrinking forces develop. When no part 81 is present, mold 80 may
be configured to withstand heating and curing cycles without such
fracturing. However, when a part 81 is present (e.g., a part
initially provided as a viscous liquid that converts to a rigid
solid during curing), the expanded dimensions of part 81 may
fracture a seal of mold 80. Such fracturing may occur when the
dimensions of the mold 80 shrink during cooling, as the cured part
81 may remain substantially the same size (e.g., experience little
or no reduction in size). In particular, the force generated
between part 81 and the shirking mold 80 may result in the fracture
of the seal (e.g., a fracture in sealing material 83). For example,
FIG. 7 illustrates a mold assembly including a mold 80 in which
sections 90 are separated and broken apart, which may occur during
cooling, as part 81 may contract at a slower rate as compared to
mold 80 or may experience substantially no contraction. This may
cause sealing material 83 to stretch or remain stretched, thereby
allowing mold 80 to conform to the size of part 81. Additionally,
sealing material 83 may be configured to maintain a vacuum while
sections 90 are separated from each other (e.g., during heating),
to the ability of sealing material 83 to seal seam 82.
[0044] In some aspects, as shown in FIG. 8, sections 90 of mold 80
may be mechanically secured or held together using one or more
resilient members such as springs 84 or other flexible means. As
shown in FIG. 8, springs 84 may be configured to allow mold
sections 90 to separate from each other upon generation of
sufficient force (e.g., as applied by part 81 to walls of mold
sections 90). In some aspects, mechanical sealing of joints of mold
80, such as a joint at seam 82, may facilitate the application of
vacuum. Such vacuum may be generated and maintained, for example,
during heating and curing of part 81 within mold 80. In the
configuration illustrated in FIG. 8, a mold assembly may include
one or more springs 84 secured to sections 90 so as to stretch as
sections 90 move away from each other due to forces applied by part
81. In particular, part 81 may be in contact with mold 80 such that
expansion of part 81 applies force to the walls of mold 80 that
define cavity 78. The force generated by contact between part 81
and mold 80 may be sufficient to cause sections 90 to move apart
along seam 82 and split mold 80 into two pieces or halves formed by
sections 90. In some aspects, the force generated by the expansion
of part 81, and contact between part 81 and mold 80, may be
sufficient to mechanically fracture and/or break the seal formed by
a frangible seal material 83. This fracture may occur during
cooling, for example.
[0045] In some aspects, part 81 (e.g., a molded thermoset part) may
have insufficient structural strength to generate a sufficiently
force to fracture seal material 83 of sealed mold 80 without
experiencing damage. For molding such parts 81, it may be
beneficial to mechanically fracture a frangible seal material 83
disposed between sections 90. An exemplary mold assembly for
providing an externally-generated force is shown in FIG. 9, for
example, in which one or more hydraulic cylinders 85 may be secured
to mold 80. However, if desired, a mechanical screw mechanism may
be secured to mold 80 instead of, or in addition to, hydraulic
cylinders 85.
[0046] As shown in FIG. 9, a hydraulic cylinder 85 (three shown in
FIG. 9) may be attached to a side surface of an outer wall of a
section 90 of mold 80. Rods 91 or other moveable members of each
hydraulic cylinder 85 may be hydraulically-driven and configured to
push against an opposite side surface of an adjacent section 90 of
mold 80 so as to separate the mold 80 into two pieces and break
seal 83. The hydraulic cylinder 85 mechanism may be configured to
separate sections 90 during cooling or at other times during a
molding process, and may thereby provide sufficient space for
thermoset part 81. One or more suitable electronically-controlled
valves and control devices may be configured to cause rods 91 of
hydraulic cylinders 85 to extend, in a controllable manner, during
cooling, so as to break or fracture seal material 83.
[0047] FIG. 10 illustrates another exemplary mold assembly for
separating sections 90 of mold 80. Mechanical devices may be
secured to mold 80 to separate mold sections 90 based on
temperatures within an autoclave generated in accordance with a
predetermined temperature profile. For example, such mechanical
devices may be configured to generate force sufficient to fracture
material 83 when exposed to elevated temperatures of such a
predetermined temperature profile.
[0048] In an exemplary mechanical device, expansion and contraction
(e.g., due to thermal cycling) of a relatively long rod 87 may
drive a scissor mechanism 86. Rod 87 may be constructed of a rigid
material that expands and contracts with changes in temperature at
a rate sufficient to drive scissor mechanism 86. A portion of
scissor mechanism 86 including rod 87 and a slide mechanism 88 may
form an actuator side of scissor mechanism 86, while a side of
scissor mechanism 86 connected to mold sections 90 may form an
actuated or driven side of scissor mechanism 86. Thus, motion of
the actuated side may cause a corresponding motion of the actuated
side to separate sections 90.
[0049] As shown in FIG. 10, rod 87 may be rotationally attached to
one side of scissor mechanism 86 (e.g., a first leg of scissor
mechanism 86 that forms an exemplary moveable member). A first end
of rod 87 may be rotationally connected to a first arm of scissor
mechanism 86. A second end of rod 87 may pass through a slide
mechanism 88 which may be rotationally attached to the other end of
the actuator side of the scissor mechanism 86 (e.g., a second leg
of scissor mechanism 86 that forms an exemplary moveable member).
Slide mechanism 88 may be configured to facilitate sliding motion
of rod 87 through the slide mechanism 88 as rod 87 moves outward
(e.g., expands so as to extend farther through slide mechanism 88)
but locks or prevents withdrawal of rod 87 when rod 87 experiences
forces that tend to pull rod 87 in an inward direction (e.g., a
direction opposite to the outward direction when rod 87
retracts).
[0050] In operation, when mold 80 and scissor mechanism 86 are
heated in an autoclave for curing part 81, rod 87 may expand (e.g.,
with slide end of rod 87), so as to expand and move through slide
mechanism 88. After reaching a maximum temperature, and, if
desired, holding the maximum temperature for a predetermined period
of time, the cure cycle may be completed and the autoclave may
begin to cool. As rod 87 cools, it may be prevented from sliding
back or retracting through the slide mechanism 88. As a result,
scissor mechanism 86, and, in particular, rod 87 and slide
mechanism 88, may be configured to create a force that tends to
pull the two ends of the actuator side of scissor mechanism 86
together. This force may cause the actuated side or opposite end of
scissor mechanism 86 to move apart. In some aspects, as the
actuated side of scissor mechanism 86 may include scissor arms
secured to each section 90 on opposite sides of mold 80, sufficient
force may be generated to separate the two halves or sections 90 of
mold 80 and thereby relieve pressure on molded thermoset part
81.
[0051] In some aspects, a method for molding a part may include
forming a plurality of mold sections 90 with the above-described
additive manufacturing apparatus. These mold sections 90 may be
connected to each other (e.g., by applying sealing material 83). If
desired, one or more separation devices such as a resilient member
84 (FIG. 8), a push-rod and/or hydraulic cylinder (FIG. 9), and a
scissor mechanism (FIG. 10), may be connected to mold 80. A part 81
may be placed in cavity 78, and the part 81 and mold 80 may be
heated (e.g., within an autoclave). Prior to and/or during this
heating, vacuum may be applied to cavity 78, the vacuum being
maintained via the seal formed by sealing material 83. This seal
may be maintained during at least a portion of a curing process of
part 81. During cooling, frangible sealing material 83 may be
fractured to break the seal by any of the mechanisms described
above.
[0052] From the foregoing detailed description, it will be evident
that there are a number of changes, adaptations and modifications
of the present disclosure which come within the province of those
persons having ordinary skill in the art to which the
aforementioned disclosure pertains. However, it is intended that
all such variations not departing from the spirit of the disclosure
be considered as within the scope thereof as limited by the
appended claims.
* * * * *