U.S. patent application number 15/728920 was filed with the patent office on 2019-04-11 for core mechanical integrity testing by viscosity manipulation.
The applicant listed for this patent is General Electric Company. Invention is credited to Paul Stephen DiMascio, Jose Troitino Lopez.
Application Number | 20190105705 15/728920 |
Document ID | / |
Family ID | 65817050 |
Filed Date | 2019-04-11 |
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United States Patent
Application |
20190105705 |
Kind Code |
A1 |
Troitino Lopez; Jose ; et
al. |
April 11, 2019 |
CORE MECHANICAL INTEGRITY TESTING BY VISCOSITY MANIPULATION
Abstract
A mold system for forming a casting article for investment
casting in which the mechanical integrity of a ceramic core can be
tested by viscosity manipulation. A method for testing a ceramic
core used for an investment casting includes: positioning the
ceramic core within a mold for receiving a sacrificial material
fluid to form a sacrificial material on at least a portion of the
ceramic core, the ceramic core having a predefined layout; during
casting of the sacrificial material fluid about the ceramic core
using the mold, controlling a viscosity of the sacrificial material
fluid to simulate an expected viscosity of a molten metal used
during a subsequent investment casting using the ceramic core; and
evaluating mechanical damage to at least one region of the ceramic
core caused by the casting of the sacrificial material fluid.
Inventors: |
Troitino Lopez; Jose;
(Greenville, SC) ; DiMascio; Paul Stephen; (Greer,
SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
65817050 |
Appl. No.: |
15/728920 |
Filed: |
October 10, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22C 9/10 20130101; B22C
7/02 20130101; B22C 9/24 20130101 |
International
Class: |
B22C 7/02 20060101
B22C007/02; B22C 9/10 20060101 B22C009/10; B22C 9/24 20060101
B22C009/24 |
Claims
1. A method for testing a ceramic core used for an investment
casting, the method comprising: positioning the ceramic core within
a mold for receiving a sacrificial material fluid to form a
sacrificial material on at least a portion of the ceramic core, the
ceramic core having a predefined layout; during casting of the
sacrificial material fluid about the ceramic core using the mold,
controlling a viscosity of the sacrificial material fluid to
simulate an expected viscosity of a molten metal used during a
subsequent investment casting using the ceramic core; and
evaluating mechanical damage to at least one region of the ceramic
core caused by the casting of the sacrificial material fluid.
2. The method of claim 1, wherein the mechanical damage includes
cracking or breaking of the ceramic core.
3. The method of claim 1, further comprising, after the evaluating,
modifying the predefined layout of the ceramic core.
4. The method of claim 3, further comprising repeating the
positioning, viscosity controlling, evaluating, and modifying until
the casting of the sacrificial material fluid does not damage the
ceramic core.
5. The method of claim 1, further comprising forming the mold by
fastening a plurality of separable mold portions together.
6. The method of claim 5, further comprising controlling a
temperature of each of the plurality of separable mold
portions.
7. The method of claim 6, wherein at least one of the plurality of
separable mold portions includes a thermal conducting conduit
therein configured to conduct a thermal fluid therethrough to
control a temperature of the at least one of the plurality of
separable mold portions, wherein controlling the viscosity of the
sacrificial material fluid includes controlling the temperature of
the at least one of the plurality of separable mold portions by
conducting the thermal fluid through the thermal conducting
conduit.
8. The method of claim 5, further comprising: heating a plurality
of flows of the sacrificial material fluid to different
temperatures to control the viscosity of each of the plurality of
flows of the sacrificial material; and directing each of the
plurality of flows of the sacrificial material fluid to a
respective separable mold portion of the plurality of separable
mold portions.
9. The method of claim 5, further comprising: heating a plurality
of flows of the sacrificial material fluid to different
temperatures to control the viscosity of each of the plurality of
flows of the sacrificial material; and directing each of the
plurality of flows of the sacrificial material fluid to a
respective separable mold portion of the plurality of separable
mold portions; wherein at least one of the plurality of separable
mold portions further includes a thermal conducting conduit therein
configured to conduct a thermal fluid therethrough to control a
temperature of the at least one of the plurality of separable mold
portions, wherein controlling the viscosity of the sacrificial
material fluid further includes controlling the temperature of the
at least one of the plurality of separable mold portions by
conducting the thermal fluid through the thermal conducting
conduit.
10. A testing system for testing a ceramic core used for an
investment casting, comprising: a mold containing the ceramic core
for receiving a sacrificial material fluid to form a sacrificial
material on at least a portion of the ceramic core, the ceramic
core having a predefined layout; a viscosity control system for
controlling a viscosity of the sacrificial material fluid during
casting of the sacrificial material fluid about the ceramic core to
simulate an expected viscosity of a molten metal used during a
subsequent investment casting using the ceramic core; and an
evaluation system for evaluating the ceramic core to identify
mechanical damage caused by the casting of the sacrificial material
fluid on at least one region of the ceramic core.
11. The testing system of claim 10, wherein the mechanical damage
includes cracking or breaking of the ceramic core.
12. The testing system of claim 11, further comprising wherein the
mold includes two or more separable mold portions fastened
together.
13. The testing system of claim 12, wherein at least one of the
separable mold portions includes a thermal conducting conduit
therein configured to conduct a thermal fluid therethrough to
control a temperature of the at least one separable mold portion,
wherein the viscosity control system includes a mold thermal fluid
controller for controlling the temperature of the at least one
separable mold portion by conducting the thermal fluid through the
thermal conducting conduit.
14. The testing system of claim 13, further comprising: a
sacrificial material fluid heating system for heating a plurality
of flows of the sacrificial material fluid to different
temperatures to control the viscosity of each of the plurality of
flows of the sacrificial material, and for directing each of the
plurality of flows of the sacrificial material fluid to a
respective separable mold portion of the mold via at least one
sacrificial material fluid input.
15. The testing system of claim 10, wherein the mold includes a
plurality of separable mold portions that are coupleable together
to create the mold and configured to form the sacrificial material
from the sacrificial material fluid about the core, wherein each of
the plurality of separable mold portions includes at least one
sacrificial material fluid input zone.
16. A method for testing a ceramic core used for an investment
casting, the method comprising: positioning the ceramic core within
a mold for receiving a sacrificial material fluid to form a
sacrificial material on at least a portion of the ceramic core, the
ceramic core having a predefined layout; and controlling the
sacrificial material fluid to simulate an expected viscosity of a
molten metal used during a subsequent investment casting using the
ceramic core.
17. The method of claim 16, further comprising evaluating
mechanical damage to the core caused by the sacrificial material
fluid, the evaluating performed before the subsequent investment
casting.
18. The method of claim 17, further comprising modifying the
predefined layout of the ceramic core based on the evaluating.
19. A method for testing a ceramic core, comprising: positioning
the ceramic core within a mold for receiving a sacrificial material
fluid to form a sacrificial material on at least a portion of the
ceramic core, the ceramic core having a predefined layout; during
casting of the sacrificial material fluid about the ceramic core
using the mold, controlling, using a viscosity control system, a
viscosity of the sacrificial material fluid to simulate an expected
viscosity of a molten metal used during a subsequent investment
casting using the ceramic core; and evaluating, using an evaluation
system, mechanical damage to at least one region of the ceramic
core caused by the casting of the sacrificial material fluid.
Description
[0001] The application is related to U.S. application Ser. No.
______, GE docket number 320860-1, GE docket number 321119-1, and
GE docket number 321121-1.
BACKGROUND OF THE INVENTION
[0002] The disclosure relates generally to investment casting, and
more particularly, to a mold system for forming a casting article
for investment casting in which the mechanical integrity of a core
(e.g., a ceramic core) can be tested by viscosity manipulation.
[0003] Investment casting is used to manufacture a large variety of
industrial parts such as turbomachine blades. Investment casting
uses a casting article having a sacrificial material pattern to
form a ceramic mold for the investment casting. Certain types of
casting articles may include a core or insert within the
sacrificial material pattern. The core defines an interior
structure of the component and becomes a part of the ceramic mold
used during the investment casting. The core can include a large
variety of intricate features that define an interior structure of
the component. Cores can be additively manufactured to allow for
rapid prototyping and manufacturing of the cores. The casting
article is made by molding a sacrificial material fluid, such as
hot wax or a polymer, about the core in a mold that defines the
shape of the component surrounding the core. The hardened
sacrificial material formed about the core defines the shape of the
component for the investment casting.
[0004] Each casting article, either individually or in a collection
thereof, can be dipped in a slurry and coated with a ceramic to
form a ceramic mold for the investment casting. Once the
sacrificial material is removed from the ceramic mold, the mold can
be used to investment cast the component using a molten metal,
e.g., after pre-heating the ceramic mold. Once the molten metal has
hardened, the ceramic mold can be removed, and the core can be
removed using a leachant. The component can then be finished in a
conventional fashion, e.g., heat treating and conventional
finishing.
[0005] Investment casting is a time consuming and expensive
process, especially where the component must be manufactured to
precise dimensions. In particular, where precise dimensions are
required, formation of the casting article must be very precise.
Each mold used to form the casting article can be very costly, and
can take an extensive amount of time to manufacture. Consequently,
any changes in the core or the component can be very expensive and
very time consuming to address. Other challenges that can be costly
and time consuming to address are unforeseen weaknesses in the core
that cause it to crack or break either during formation of the
casting article (e.g., during casting of the sacrificial material
about the core), or during the actual investment casting. For
example, high pressure sacrificial fluid injected into a mold about
the core during casting article formation can crack or break the
core, or molten metal injected during the investment casting can
crack or break the core. In the former case, the core must be
adjusted, and in the latter case, the core and/or the casting
article mold may need adjusting. In any event, the changes are
costly and time consuming. Currently, there is no mechanism to
proactively address the core cracking/breaking challenges.
[0006] One approach to reduce time and costs employs additive
manufacture of the cores and molds for making the casting article.
In particular, additive manufacture allows for more rapid
turnaround for design changes in cores and/or the component leading
up to the component manufacturing steps. Additive manufacturing
(AM) includes a wide variety of processes of producing an object
through the successive layering of material rather than the removal
of material. Additive manufacturing can create complex geometries
without the use of any sort of tools, molds or fixtures, and with
little or no waste material. Instead of machining objects from
solid billets of material, much of which is cut away and discarded,
the only material used in additive manufacturing is what is
required to shape the object. Current categories of additive
manufacturing may include: binder jetting, material extrusion,
powder bed infusion, directed energy deposition, sheet lamination
and vat photopolymerization.
[0007] Additive manufacturing techniques typically include taking a
three-dimensional (3D) computer aided design (CAD) file of the
object (e.g., core and/or casting article mold) to be formed,
electronically slicing the object into layers (e.g., 18-102
micrometers thick) to create a file with a two-dimensional image of
each layer (including vectors, images or coordinates) that can be
used to manufacture the object. The 3D CAD file can be created in
any known fashion, e.g., computer aided design (CAD) system, a 3D
scanner, or digital photography and photogrammetry software. The 3D
CAD file may undergo any necessary repair to address errors (e.g.,
holes, etc.) therein, and may have any CAD format such as a
Standard Tessellation Language (STL) file. The 3D CAD file may then
be processed by a preparation software system (sometimes referred
to as a "slicer") that interprets the 3D CAD file and
electronically slices it such that the object can be built by
different types of additive manufacturing systems. The object code
file can be any format capable of being used by the desired AM
system. For example, the object code file may be an STL file or an
additive manufacturing file (AMF), the latter of which is an
international standard that is an extensible markup-language (XML)
based format designed to allow any CAD software to describe the
shape and composition of any three-dimensional object to be
fabricated on any AM printer. Depending on the type of additive
manufacturing used, material layers are selectively dispensed,
sintered, formed, deposited, etc., to create the object per the
object code file.
[0008] One form of powder bed infusion (referred to herein as metal
powder additive manufacturing) may include direct metal laser
melting (DMLM) (also referred to as selective laser melting (SLM)).
This process is advantageous for forming metal molds for forming
casting articles. In metal powder additive manufacturing, metal
powder layers are sequentially melted together to form the object.
More specifically, fine metal powder layers are sequentially melted
after being uniformly distributed using an applicator on a metal
powder bed. Each applicator includes an applicator element in the
form of a lip, brush, blade or roller made of metal, plastic,
ceramic, carbon fibers or rubber that spreads the metal powder
evenly over the build platform. The metal powder bed can be moved
in a vertical axis. The process takes place in a processing chamber
having a precisely controlled atmosphere. Once each layer is
created, each two dimensional slice of the object geometry can be
fused by selectively melting the metal powder. The melting may be
performed by a high powered irradiation beam, such as a 100 Watt
ytterbium laser, to fully weld (melt) the metal powder to form a
solid metal. The irradiation beam moves or is deflected in the X-Y
direction, and has an intensity sufficient to fully weld (melt) the
metal powder to form a solid metal. The metal powder bed may be
lowered for each subsequent two dimensional layer, and the process
repeats until the object is completely formed. In order to create
certain larger objects faster, some metal additive manufacturing
systems employ a pair of high powered lasers that work together to
form an object, like a mold. Other additive manufacturing
processes, such as 3D printing, may form layers by dispensing
material in layers.
[0009] Although additive manufacturing of cores and/or molds for
casting article formation has reduced time and cost for adjusting
cores and/or molds, challenges remain. Most notably, current mold
systems and practices for forming a casting article form one mold
regardless of variations in cores. When variations in cores are
subtle or when the core has fine or intricate features, it can
result in cracked or broken cores and/or imprecise casting
articles. Where variations in cores are more profound, e.g., where
they share a common structure but also have other structure that
varies widely to build different components, each variation of core
must have its own mold. Current mold systems used for forming the
casting articles are also not sufficiently thermally adjustable to
accommodate sacrificial material fluid flow across different
cores.
[0010] Another challenge with current investment casting is
ensuring cores within a casting article can withstand the actual
investment casting, i.e., the casting of a molten metal about the
core. The current practice includes a trial and error approach in
which a casting article is used to perform an investment casting to
determine its efficacy. During investment casting, the core may,
for example, break, crack or prevent adequate molten metal flow to
form the component. In the absence of any mechanism to predict core
efficacy, when a problem is identified during investment casting,
changes to the core, the metal casting article mold, and/or the
casting article formation process must be made, all of which are
time consuming and expensive.
BRIEF DESCRIPTION OF THE INVENTION
[0011] A first aspect of the disclosure provides a method for
testing a ceramic core used for an investment casting. The method
includes: positioning the ceramic core within a mold for receiving
a sacrificial material fluid to form a sacrificial material on at
least a portion of the ceramic core, the ceramic core having a
predefined layout; during casting of the sacrificial material fluid
about the ceramic core using the mold, controlling a viscosity of
the sacrificial material fluid to simulate an expected viscosity of
a molten metal used during a subsequent investment casting using
the ceramic core; and evaluating mechanical damage to at least one
region of the ceramic core caused by the casting of the sacrificial
material fluid.
[0012] A second aspect of the disclosure provides a system for
system for testing a ceramic core used for an investment casting,
including: a mold containing the ceramic core for receiving a
sacrificial material fluid to form a sacrificial material on at
least a portion of the ceramic core, the ceramic core having a
predefined layout; a viscosity control system for controlling a
viscosity of the sacrificial material fluid during casting of the
sacrificial material fluid about the ceramic core to simulate an
expected viscosity of a molten metal used during a subsequent
investment casting using the ceramic core; and an evaluation system
for evaluating the ceramic core to identify mechanical damage
caused by the casting of the sacrificial material fluid on at least
one region of the ceramic core.
[0013] A third aspect of the disclosure includes a method for
testing a ceramic core used for an investment casting, the method
including: positioning the ceramic core within a mold for receiving
a sacrificial material fluid to form a sacrificial material on at
least a portion of the ceramic core, the ceramic core having a
predefined layout; and controlling the sacrificial material fluid
to simulate an expected viscosity of a molten metal used during a
subsequent investment casting using the ceramic core.
[0014] The illustrative aspects of the present disclosure are
designed to solve the problems herein described and/or other
problems not discussed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] These and other features of this disclosure will be more
readily understood from the following detailed description of the
various aspects of the disclosure taken in conjunction with the
accompanying drawings that depict various embodiments of the
disclosure.
[0016] FIG. 1 shows a perspective front view of a mold system
according to embodiments of the disclosure.
[0017] FIG. 2 shows a perspective rear view of a mold system
according to embodiments of the disclosure.
[0018] FIG. 3 shows a front, see-through perspective view of the
mold system according to embodiments of the disclosure.
[0019] FIG. 4 shows a side, see-through perspective view of the
mold system according to embodiments of the disclosure.
[0020] FIGS. 5-7 show schematic side views of illustrative varied
cores.
[0021] FIG. 8 show a schematic top view of illustrative overlaid
varied cores.
[0022] FIG. 9 shows a cross-sectional top view of a first core in a
mold system including separable mold portions according to
embodiments of the disclosure.
[0023] FIG. 10 shows a cross-sectional top view of a second,
different core from that of FIG. 9 in a mold system including
different separable mold portions according to embodiments of the
disclosure.
[0024] FIG. 11-14 show varied views of a pair of separable mold
portions of a mold system according to embodiments of the
disclosure.
[0025] FIGS. 15-18 show varied views of another pair of separable
mold portions of a mold system according to embodiments of the
disclosure.
[0026] FIG. 19 shows a perspective view of an illustrative core
positioner according to one embodiment of the disclosure.
[0027] FIG. 20 shows a schematic, cross-sectional view of an
illustrative mold system including a mold thermal fluid controller
for delivering temperature controlled thermal fluid to mold thermal
conducting conduits in the mold, and showing varied mold thermal
conducting conduit paths and positions according to various
embodiments of the disclosure.
[0028] FIG. 21 shows a schematic, cross-sectional view of an
illustrative mold system including a sacrificial material heating
system according to various embodiments of the disclosure.
[0029] FIG. 22 shows a flow diagram illustrating methods according
to various embodiments of the disclosure.
[0030] FIG. 23 depicts an investment casting process including
ceramic core mechanical integrity testing by viscosity manipulation
according to various embodiments of the disclosure.
[0031] FIG. 24 depicts a process for ceramic core mechanical
integrity testing by viscosity manipulation according to various
embodiments.
[0032] It is noted that the drawings of the disclosure are not
necessarily to scale. The drawings are intended to depict only
typical aspects of the disclosure, and therefore should not be
considered as limiting the scope of the disclosure. In the
drawings, like numbering represents like elements between the
drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0033] As indicated above, the disclosure provides a mold system
including a mold for receiving therein a selected core chosen from
a plurality of varied cores. The mold is configured to form a
sacrificial material from a sacrificial material fluid, e.g., wax
or a polymer, about a selected core to create a casting article.
The casting article including the core and hardened sacrificial
fluid material thereabout are used in a conventional manner to form
a ceramic mold used for subsequent investment casting of a
component. The varied cores may differ in any number of ways such
as shape, dimensions, contours, material properties, etc. In one
example, each varied core can be close in shape, but have some
dimensional variance. In another example, part of a casting article
mold may be employed to form a number of components that share a
common, first internal structure formed by a common core, but
include a number of different, second internal structures formed by
a second, different core. That is, the common, first internal
structure may be formed by a first, common core, while the
different, second internal structures may be made by various second
cores. The cores may be made from ceramic or other refractory
material (e.g., niobium, molybdenum, tantalum, tungsten or
rhenium), metal, metal alloy or combinations thereof.
[0034] In order to address the challenge of varied cores, a mold
according to embodiments of the disclosure includes a plurality of
separable mold portions that are coupleable together to create the
mold. In contrast to conventional mold systems, at least one
selected separable mold portion of the plurality of separable mold
portions includes a set of varied interchangeable versions of the
at least one selected separable mold portion. Each varied
interchangeable version of the selected separable mold portion is
configured to accommodate a different core of the plurality of
varied cores. In this fashion, variations in cores, whether simple
dimensional differences or widely different internal structures to
create different components, can be readily accommodated without
forming a complete, expensive metal mold for each core variation.
Embodiments of the disclosure also leverage the separable mold
portions to provide precise temperature control across the mold to
address a number of issues such as certain core areas being prone
to cracking or breaking.
[0035] Referring to FIGS. 1 and 2, a front perspective view and a
rear perspective view, respectively, of a mold system 100 according
to embodiments of the disclosure are illustrated. Further, FIG. 3
shows a front, see-through perspective view, and FIG. 4 shows a
side, see-through perspective view of mold system 100 from FIGS.
1-2. It is appreciated that according to embodiments of the
disclosure, mold system 100 is used for forming a casting article
102 (FIGS. 3-4) for investment casting. For purposes of
description, as shown in FIGS. 3-4, the disclosure shows the
component to be built as a turbomachine airfoil 104. It will be
readily understood that the teachings of the disclosure are
applicable to any component capable of investment casting and which
is to include an internal structure formed by a core.
[0036] Mold system 100 includes a mold 110 for receiving therein a
selected core chosen from a plurality of varied cores. The
variation in cores can take any of a large number of forms. In the
example shown in FIGS. 3 and 4, two different cores 112A, 112B
(collectively "cores 112") are illustrated that collectively form
an internal structure in the turbomachine airfoil, e.g., cooling
channels, support structure, etc. In the turbomachine airfoil
example, a core 112A may form a portion including a leading edge of
the airfoil, while core 112B forms a portion including a trailing
edge of the airfoil. In one non-limiting example, a number of
different turbomachine airfoils can be formed by using a single
leading edge core 112A, and a variety of different, trailing edge
cores 112B. FIGS. 5-7 show schematic side views of a number of
examples in which single leading edge core 112A is used, and a
variety of differently shaped cores 112B are employed. It is
recognized that the portion of the component that changes can also
differ from component to component, e.g., for an airfoil, the
leading edge or a root portion 118 may also vary.
[0037] FIG. 8, in contrast to FIGS. 5-7, shows a top view of varied
cores 112A, 112B in which the difference is simply a dimensional or
shape variation created by variation during core manufacture, e.g.,
via additive manufacturing. In this setting, variations from core
to core can be identified in any now known or later developed
fashion such as but not limited to: blue light scans or point cloud
scans. The differences identified can be used to generate a model
of the actual cores 112A, 112B, which can then be used to adjust
mold 110 accordingly, e.g., to maintain a desired spacing between
and interior surface 132 of mold 110 and core 112 to ensure proper
positioning and thickness of sacrificial material 130.
Modifications to mold 110 can be made during manufacturing of the
mold (e.g., using additive manufacturing and/or computer aided
design software systems), and in particular, separable mold
portions 120 that form the mold. Core 112 can be formed in any now
known or later developed fashion. In one embodiment, core 112 is
formed by additive manufacturing, e.g., 3D printing.
[0038] Mold 110 includes a plurality of separable mold portions
120A-D (collectively "separable mold portions 120") that are
coupleable together to create the mold. As shown in FIGS. 1-4, four
mold portions 120A-D are provided in the example shown. It is
understood however that any number of separable mold portions 120
may be employed, e.g., two or more. As understood, mold 110 is
configured to form sacrificial material 130 from a sacrificial
material fluid (i.e., sacrificial material in a fluid form) about a
selected core 112. Core 112 is positioned within mold 110 and is
spaced from interior surface 132 of mold 110 such that sacrificial
material fluid can readily flow between core 112 and the interior
surface of the mold to create casting article 102. The sacrificial
material can be any now known or later developed material that is
capable of injecting in a fluid form, and that is sufficiently
rigid in a solid state to hold its shape during investment casting
ceramic mold formation. Sacrificial material may include but is not
limited to: wax or polymer.
[0039] As shown in FIGS. 9 and 10, any selected separable mold
portion 120 of plurality of separable mold portions 120A-D in a
particular mold can include a set of varied interchangeable
versions thereof. In the example shown, a set of separable mold
portions 120E (FIGS. 9) and 120F (FIG. 10) are provided for a
portion including a trailing edge of a turbomachine airfoil 104.
While two varied interchangeable versions are shown, any number may
be employed to accommodate any number of varied cores 112, e.g.,
sets with many similar mold portions can be made. Each varied
interchangeable version 120E, 120F of the selected separable mold
portion 120 may be configured to accommodate a different core 112
of the plurality of varied cores 112. In the example shown in FIG.
9, a separable mold portion 120E is shaped to accommodate core
112B, while as shown in FIG. 10, separable mold portion 120F is
shaped to accommodate different core 112A in the same position of
mold 110. Each varied interchangeable version of a selected
separable mold portion 120 can be different in a number of ways
such as but not limited to: mold opening shape, size: length,
width, height; thermal cooling circuit (presence or path, described
elsewhere herein); coefficient of thermal expansion; coefficient of
heat transfer; material and/or material properties such as yield
strength, grain boundary structure, surface finish, etc. In any
event, selected separable mold portions 120E, 120F are configured
to be positioned in the same position within mold 110 to complete
the mold, but have different interior surfaces 132 to accommodate
varied cores 112A, 112B. As will be described herein, separable
mold portions 120E, 120F may include a number of other features
that allow for, among other things, proper coupling and thermal
control.
[0040] Each separable mold portion 120 may include a metal alloy,
an acrylic based material such as but not limited to poly-methyl
methylacrylate (PMMA), or a material having glass transition
temperature above 70.degree. C. (approximately 160.degree. F.).
Where a metal alloy is employed, separable mold portions 120 can be
readily manufactured with the afore-mentioned customized structure
using, for example, additive manufacturing. More particularly, a
metal powder additive manufacturing process may be used to form
metal separable mold portions 120. Metal powder additive
manufacturing may include, for example, direct metal laser melting
(DMLM). It is understood that the general teachings of the
disclosure are equally applicable to other forms of metal powder
additive manufacturing such as but not limited to direct metal
laser sintering (DMLS), selective laser sintering (SLS), electron
beam melting (EBM), and perhaps other forms of additive
manufacturing. Where separable mold portions 120 include an
acrylic-based material or material with glass transition
temperature above 70.degree. C., mold portions 120 can be
manufactured by, for example, stereolithography or 3D printing
(e.g., using stereolithography resins). Other processes may also be
employed to manufacture separable mold portions 120, e.g., casting
and machining.
[0041] FIGS. 11-14 show various views of selected separable mold
portions 120C, 120D from a top portion of mold 110 in FIGS. 1-4,
and FIGS. 15-18 show various views of selected separable mold
portions 120A, 120B from a bottom portion of mold 110 in FIGS. 1-4.
More particularly, FIGS. 11 and 12 show perspective views of mating
separable mold portions 120C, 120D; FIG. 13 shows a bottom view of
both mold portions 120C, 120D; FIG. 14 shows a perspective view of
both mold portions 120C, 120D; FIGS. 15 and 16 show perspective
views of mating separable mold portions 120A, 120B; FIG. 17 shows a
side view of both mold portions 120A, 120B; and FIG. 18 shows a
perspective view of both mold portions 120A, 120B. As illustrated,
each separable mold portion 120 may include any structure necessary
for sealingly coupling with other mold portions. For example, mold
portions 120A-D may include mating surfaces 136 configured to seat
and mate with an adjacent mold portion. Surfaces 136 can be any
shape necessary to allow mating, e.g., planar and/or curved.
Surfaces 136 are dimensioned so as to prevent sacrificial material
130 fluid from passing therethrough when mated. Further, certain
mold portion(s) 120A-D may include gasket grooves 138 (FIGS. 13,
15-18) configured to receive a gasket (not shown) therein for
sealing with an adjacent mold portion. Further, certain mold
portion(s) 120C-D may include ceramic core top-bot fixturing ends
140. Separable mold portions 120A, 120B, 120C, 120D are also
designed to be mixed and matched, for example separable mold
portions 120A and 120B forming a bottom portion of mold 110 may be
common across multiple airfoil designs having differing separable
mold portions 120C, 120D that form top portion of mold 110.
[0042] Certain mold portion(s) 120A-D may also include a core
positioner receiver 144 therein. Each core positioner receiver 144
is configured to receive a core positioner 146 (FIGS. 2 and 19)
therein that extends through a respective mold portion 120 to
contact and appropriately position a respective core 112 relative
to interior surface 132 of mold 110. That is, position core 112
spaced from an interior surface 132 of mold 110 to define the
position and thickness of sacrificial material 130 about the core.
Core positioner receivers 144 are thus another feature of each
separable mold portion 120 that can be varied to accommodate varied
cores 112. Each core positioner receiver 144 may include a hole
extending from interior surface 132 of mold 110 to an exterior
surface 145 of mold 110, and may include a counter-bore on the
external surface of mold 110. Mold system 100 may include a
plurality of core positioners 146 (FIG. 2) configured to position
the selected core 112 via core positioner receivers 144 in the at
least one of the plurality of separable mold portions 120. In one
embodiment, each core positioner 146 (FIG. 2) may have a selected
length to position a respective portion of a selected core 112
relative to interior surface 132 of mold 110. In this case, a set
of core positioners 146 (FIG. 2) may be provided for each mold
portion 120 and/or for each varied core 112. In another embodiment,
core positioner 146 (FIG. 19) may be adjustable in each core
positioner receiver 144 so as to accommodate a variety of mold
portions 120 and/or a number of varied cores 112. For example, as
shown in FIG. 19, a core positioner 146 may include a head 148
coupled to a rod 150. Head 148 may be threaded so as to mate and
adjustably seat in a counter-threaded core positioner receiver 144
in a separable mold portion 120. As head 148 is threadably
inserted, the positon of rod 150 relative to interior surface 132
changes to accommodate contact with rod 150 with an external
surface of different cores 112. Head 148 may include any structure
necessary to allow for the adjustment, e.g., a screwdriver head. In
this fashion, each adjustable core positioner 146 (FIG. 19) may be
configured to position a number of the plurality of varied cores
112 in mold 110.
[0043] Returning to FIGS. 11-18, certain separable mold portions,
e.g., 120A in FIG. 15, may include air flow path(s) 152 to allow
air to exit mold 110. Air flow path(s) 152 may be provided wherever
necessary to ensure air removal during operation.
[0044] Referring to FIGS. 1, 2 and 14-18, plurality of separable
mold portions 120A-D may be fastened together in a number of ways.
As shown in FIGS. 1 and 2, fasteners 160 may be used to selectively
couple plurality of separable mold portions together, e.g., 120B to
120D and 120A to 120C. Fasteners 160 can take any form to hold mold
portions 120A-D together during operation, e.g., external clamps
held in position by bolts, seats in mold portions (shown), screws,
etc. Certain separable mold portions 120A-D may also include mating
fastener holes 162 for receiving a fastener (not shown) therein,
e.g., threaded bolt, screw, etc., to selectively fasten mold
portions together. For example, as shown in FIGS. 11 and 12,
separable mold portions 120C and 120D may include mating fastener
holes 162, and as shown in FIGS. 15 and 16, separable mold portions
120A and 120B may include mating fastener holes 162. Mating
fastener holes 162 (in one or both separable mold portions being
fastened) may include a mechanism to secure the fastener, e.g.,
mating threads, locking seat, etc. In addition to individual
fastening of separable mold portions 120A-D, any now known or later
developed mold locking press may be employed to further hold mold
110 together during use.
[0045] Mold system 100 also provides mechanisms for controlling a
temperature of mold 110. In particular, separable mold portions 120
provide for more precise thermal control than conventional systems.
Temperature control of mold 110, and in particular each separable
mold portion 120 or a zone including a certain separable mold
portion 120 may be desired for a number of reasons. For example,
temperature control allows one to: maintain a desired viscosity
and/or temperature of sacrificial material fluid, maintain a
desired temperature of a core 112, protect mold 110 from
overheating damage, and preheat mold 110 to ensure proper casting.
Further, certain sacrificial material fluids, e.g., wax or certain
polymers, may require a certain temperature to create a fluid form
and/or maintain an appropriate temperature for creating casting
article 102. As will be described, the temperature control can be
customized and controlled in a number of ways according to
embodiments of the disclosure.
[0046] In one embodiment, as shown for example in FIGS. 11, 12, 15
and 16, each separable mold portion 120A-D may also include a mold
thermal conducting conduit 164 therein configured to conduct a
temperature controlled thermal fluid therethrough to control a
temperature of at least the respective separable mold portion 120.
Mold thermal conducting conduits 164 may be deemed "closed loop"
because they are arranged to provide a complete path followed by
temperature controlled thermal fluid 176 as it is fed from mold
thermal fluid controller 180 to input port(s), through the
respective portion of mold portion(s) 120A-D and then to output
port(s). Temperature controlled thermal fluid 176 used can be any
now known or later developed heat conducting fluid, e.g., air,
water, antifreeze, etc., appropriate for the mold material.
Temperature controlled thermal fluid 176 may add heat to a
respective separable mold portion 120A-D, and/or cool it.
Temperature controlled thermal fluid 176 may be used to preheat
mold 110 and/or maintain a temperature during casting article 102
formation. It is recognized that while temperature controlled
thermal fluid 176 passes through a respective separable mold
portion 120A-D, it may transfer thermal energy not just to/from the
particular mold portion through which it passes but also to
neighboring structure, the sacrificial material fluid and/or core
112.
[0047] Each varied interchangeable version of the at least one
selected separable mold portion 120A-D may include a mold thermal
conducting conduit 164 different than the mold thermal conducting
conduit in the other separable mold portions of the set. In this
manner, each version of a selected separable mold portion 120A-D
can have its respective thermal conducting path customized for the
situation for which the mold portion is built. For example, as
shown in FIG. 9, a certain core 112B may require mold thermal
conducting conduits 164 that pass in close proximity to interior
surface 132 to maintain the core and/or sacrificial material 130
fluid at a certain desired temperature, e.g., less than 0.5
centimeters. In contrast, as shown in FIG. 10, another core 112B
may have mold thermal conducting conduits 164 that do not pass as
close to interior surface 132, e.g., greater than 0.5 centimeters.
Again, each separable mold portion 120A-D and any mold thermal
conducting conduits 164 therein can be customized for the expected
situation for which it was built. The customization of mold thermal
conducting conduits 164 can take any form including but not limited
to: conduit number, cross-sectional area, length, shape,
position/path, etc., and temperature controlled thermal fluid
temperature, type, flow rate, etc.
[0048] FIG. 20 shows a schematic, cross-sectional view of a mold
110 including various mold thermal conducting conduits 164A-E
illustrating example paths and/or positions at which they can be
employed. As shown in FIG. 20, mold thermal conducting conduit(s)
164A-E (collectively "mold thermal conducting conduits 164") may
take any path through a respective mold portion including but not
limited to: straight line 164A, curved line 164B, loop(s) 164C,
helical or spiral 164D, sinusoidal 164E, etc. As also shown in FIG.
20, not all separable mold portions 120 need include a mold thermal
conducting conduit, e.g., portion 120K is devoid of conduits. As
also shown in FIG. 20, external mold thermal conducting conduit(s)
168 may also be provided to route conduit paths on exterior surface
145 of, e.g., mold portion(s) 120M. Any now known or later
developed ports 170 can be provided on exterior surface 145 of mold
portion(s) 120 for fluidly coupling to external conduits 174 (one
example shown in FIG. 20) that fluidly communicate with a mold
thermal fluid controller 180 configured to control a temperature of
each of the plurality of separable mold portions 120K-N or a zone
including a portion of selected separable mold portions.
[0049] Mold thermal fluid controller 180 can include any now known
or later developed temperature controlled thermal fluid temperature
control system for creating any number of temperature controlled
thermal fluid 176 flows, each at a specific temperature, e.g., a
multi-tiered heat exchanger such as Thermolater TW Series water
temperature control unit. Any necessary pumps to move temperature
controlled temperature controlled thermal fluid 176 may also be
provided. Mold thermal conducting conduits 164 can be arranged to
control the temperature of a particular separable mold portion 120
and/or a sacrificial material fluid input zone 190. With regard to
the zones, one or more mold thermal conducting conduit(s) 164 may
act to control a temperature of a defined sacrificial material
fluid input zone 190A-C (3 shown). Each zone 190A-C is configured
to receive a sacrificial material fluid to form a sacrificial
material about the core at a particular temperature. Each zone
190A-C can be defined by, for example, any desired area and/or
volume of mold 110, any area and/or volume of the void to be filled
by sacrificial material 130 fluid, and/or any area and/or volume of
core 112. Each separable mold portion 120A-C may include at least
one sacrificial material fluid input zone 190A-C, i.e., zones do
not necessarily match mold portions.
[0050] At least one separable mold portion 120 can have temperature
controlled thermal fluid 176 passing therethrough having a
temperature different than another separable mold portion 120.
Similarly, each zone 190A-C can have temperature controlled thermal
fluid 176 passing through or near in such a way as to have a
temperature different than another zone. In any event, a mold
thermal conducting conduit 164 may control a temperature of at
least the sacrificial material 130 fluid within at least one
respective separable mold portion 120, and perhaps other areas such
as those downstream of the mold portion in which the conduit
exists. Each zone 190A-C, for example, can have a temperature
controlled therein to control, for example, the viscosity and other
flow characteristics of sacrificial material 130 fluid in the
respective zone to accommodate any casting/injection issues
specific to that zone including but not limited to: difficult
wetting/flow conditions, and/or core 112 issues. For example, the
temperature of a zone 190A-C can be controlled based on a
characteristic of core 112, e.g., fragility, difficult wetting,
etc., in the respective zone. In this manner, core 112 damage and
sacrificial material fluid flow can be readily controlled, and
quality casting article 102 formation can be attained. Further,
certain mold 110 materials may require using sacrificial material
fluid having a certain maximum temperature that does not damage the
mold, e.g., a PMMA mold. Each zone 190A-C temperature can also be
controlled to prevent mold damage by sacrificial material fluid
overheating. The temperature of each mold portion 120 can be
similarly controlled.
[0051] Turning to FIG. 21, a schematic cross-sectional view of a
mold system 200 according to a further embodiment of the disclosure
is illustrated. Mold system 200 may be substantially similar to
mold system 100 as described herein. For example, mold system 200
includes a mold 210 for receiving therein core 112, and mold 210
includes plurality of separable mold portions 120A-D that are
coupleable together to create the mold and configured to form the
sacrificial material from the sacrificial material fluid about the
core. Further, a selected separable mold portion, e.g., 120E, F
(FIGS. 9-10), of the plurality of separable mold portions 120
includes a set of varied interchangeable versions of the at least
one selected separable mold portion. Each varied interchangeable
version of the selected separable mold portion 120 may be
configured to accommodate a different core 112 of a plurality of
varied cores. In the FIG. 21 embodiment, however, mold system 200
may have more than one sacrificial material fluid input 284 thereto
for receiving more than one sacrificial material fluid flow 286A-C.
For example, each separable mold portion 120 may have one or more
sacrificial material fluid inputs 284. Also, some separable mold
portions 120 may be devoid of sacrificial material fluid inputs,
e.g., portion 120A in the example of FIG. 21.
[0052] In addition, mold system 200 may also include a sacrificial
material fluid heating system 202 to control the temperature and
viscosity of sacrificial material 130 fluid, and indirectly control
the temperature of mold portions 120. Sacrificial material heating
system 20 can operate alone or in addition to mold thermal fluid
controller 180 (latter shown in simpler fashion in FIG. 21 than in
FIG. 20 for clarity). Sacrificial material fluid temperature
control can be made based on separable mold portions 120 and/or
zones. Regarding zones, mold system 200 may include plurality of
sacrificial material fluid input zones 290A-C configured to receive
a sacrificial material fluid 286A-C flows to form a sacrificial
material 130 about the core. One or more sacrificial material
inputs 284A-C alone or in conjunction with mold thermal conducting
conduits 164A-E (FIG. 20) may act to control a temperature of a
sacrificial material fluid input zone 290A-C (3 shown) configured
to receive a sacrificial material fluid to form a sacrificial
material about the core. As noted, each zone 290A-C can be defined
by, for example, any desired area and/or volume of mold 210, any
area and/or volume of the void to be filled by sacrificial material
fluid, and/or any area and/or volume of core 112. Each separable
mold portion 120A-D may include at least one sacrificial material
fluid input zone 290A-C. Each zone 290A-C can have a temperature of
sacrificial material fluid injected therein (and/or temperature
controlled thermal fluid sent therethrough) controlled to control,
for example, the viscosity and other flow characteristics of
sacrificial material 130 fluid in the respective zone to
accommodate any injection issues therein including but not limited
to: difficult wetting/flow conditions, and/or core 112 issues. The
temperature of the sacrificial material fluid received in each
sacrificial material fluid input zone 290A-C may be based on, for
example, a characteristic of core 112, e.g., fragility, difficult
wetting, etc., in the respective sacrificial material input zone.
Sacrificial material 130 fluid flows 286A-C can also be controlled
based on the separable mold portions 120A-D into which they are
injected.
[0053] Sacrificial material fluid heating system 202 may include
any now known or later developed sacrificial material heating
unit(s) for creating a sacrificial material fluid flows 286A-C at a
specific temperature, e.g., a multi-tiered heat exchanger, or a
series of heating units. In the latter example, for use with wax,
heating system 202 may include a series of Dura-Bull air pressure
wax injectors, each creating fluid wax at a different temperature.
In any event, sacrificial material fluid heating system 202 may be
configured to heat a plurality of flows 286A-C of the sacrificial
material fluid to different temperatures. That is, each sacrificial
material fluid flow 286A-C may have a different temperature as
controlled by sacrificial material fluid heating system 202. In
this manner, one sacrificial material fluid input zone 290A may
receive one of the plurality of flows of the sacrificial material
fluid flows 286A at a first temperature, and another sacrificial
material fluid input zone 290B receives another sacrificial
material fluid flow 286B at a second, different temperature.
Alternatively, one separable mold portion 120C may receive one of
sacrificial material fluid flow 286A at a first temperature, and
another separable mold portion 120B may receive another sacrificial
material fluid flow 286C at a second, different temperature. The
temperatures can be selected to address any of the afore-mentioned
reasons for having temperature control.
[0054] In operation, as shown in the flow diagram of FIG. 22, a
method of forming casting article 102 for investment casting
according to embodiments of the disclosure may include, in process
P1, having a plurality of separable mold portions 120 for mold 110
for forming casting article 102 additively manufactured, e.g., by
DMLM, stereolithography, etc. As noted, plurality of mold portions
120A-D may include a set of varied interchangeable versions of a
selected separable mold portion, e.g., 120A, 120B, 120C or 120D
(FIG. 1-2), or 120K, 120L, 120M or 120N (FIG. 20). Each varied
interchangeable version of the selected separable mold portion 120
may be configured to accommodate a different core 112 of a
plurality of varied cores (FIGS. 9, 10).
[0055] As described, as shown in process P2, mold 110 may be formed
about a selected core 112 of the plurality of varied cores 112 by
coupling two or more mold-selected separable mold portions 120
together. The mold-selected separable mold portions, i.e., those
from the set(s) selected to be used in mold 110, are selected to
accommodate the selected core of the plurality of varied cores.
Each separable mold portion 120 may include a mold thermal
conducting conduit 164 therein configured to conduct temperature
controlled thermal fluid 176 (FIG. 20) therethrough to control a
temperature of at least the respective separable mold portion, or a
zone 190 in the mold. Mold 110 formation may include fastening the
two or more mold-selected separable mold portions together using
fasteners 160. Mold 110 formation may also include positioning
selected core 112 in mold 110 using a core positioner receiver 144
in at least one of the plurality of separable mold portions. The
positioning may include using a plurality of core positioners 146
(FIG. 2) configured to position selected core 112 via core
positioner receiver 144 in the at least one of the plurality of
separable mold portions 120. That is, selecting which from a
plurality of positioners 146 (FIG. 2) work for a particular core
112. Alternatively, the positioning may include using an adjustable
core positioner 146 (FIG. 19) in each core positioner receiver 144.
Each adjustable core positioner 146 is configured to position a
number of the plurality of varied cores 112 in the mold.
[0056] Once mold 110 is formed, in process P3, casting article 102
can be casted by introducing a sacrificial material 130 fluid into
the mold and about the selected core. Process P3 may further
include controlling a temperature of a plurality of sacrificial
material fluid input zones 190A-C (FIG. 20), 290A-C (FIG. 21) in
mold 110, 210, respectively. Each zone is defined to receive the
sacrificial material 130 fluid to form a sacrificial material about
the core that is positioned within the mold at a particular
temperature. Temperature of each separable mold portion 120A-D
(FIGS. 1-2) may also be controlled. As shown in FIG. 22, process P3
may include controlling a temperature of each of the plurality of
separable mold portions and/or zones, e.g., using mold thermal
fluid controller 180 alone. Alternatively, as shown in FIG. 22,
process P3 may include heating a plurality of flows 286A-C (FIG.
21) of the sacrificial material fluid to different temperatures,
e.g., using sacrificial material fluid heating system 202, and
directing one of the plurality of flows of the sacrificial material
fluid, e.g., 286C, at a first temperature to a first sacrificial
material input zone 290C of the mold, and directing another of the
plurality of flows of sacrificial material fluid, e.g., 286B, at a
second, different temperature to a second, different sacrificial
material fluid input zone 290B. Alternatively, process P3 may
include directing one of the plurality of flows of the sacrificial
material fluid, e.g., 286B, at a first temperature to a first
separable mold portion 120D of the mold, and directing another of
the plurality of flows of sacrificial material fluid, e.g., 286C,
at a second, different temperature to a second, different separable
mold portion 120B. Process P3 may also include using mold thermal
fluid controller 180 to control zone(s) 190A-C temperature, and
sacrificial material fluid heating system 202 to control
sacrificial material fluid temperature in zone(s) 290A-C. Zones
190A-C as defined for controller 180, and zones 290A-C as defined
for system 202 can be, but do not need to be, identical.
[0057] Once casting article 102 is formed, mold 110 may be removed
in any now known or later developed fashion, e.g., by unfastening
mold portions 120. As described, casting article 102 can be used in
any now known or later developed investment casting process.
[0058] Mold systems 100, 200 as described herein provide a number
of advantages compared to conventional systems. Mold systems 100,
200 allow for lower pressure sacrificial material fluid injection,
e.g., 34.5 kiloPascals (kPa) to 344.5kPa (5-50 psi), compared to
conventional systems, e.g., at or above 13.8 megaPascals (MPa).
Mold systems 100, 200 also allow for injection at optimized
sacrificial material fluid temperatures and viscosities since the
molds have their own respective temperature control. The optimized
sacrificial fluid temperatures and viscosities and injection
pressures prevent mold 110, 210 and core 112 damage due to thermal
and pressure stresses. Mold systems 100, 200 also provides modular
and customizable molds to handle a variety of cores. Separable mold
portions 120 can be reused, as necessary. Mold thermal fluid
controller 180 can be used to pre-heat molds 110, 210 directly and
cores 112 indirectly, which aids in improving the quality of
casting article 102. Mold thermal fluid controller 180 also allows
for precise temperature control of defined zones and/or separable
mold portions to address injection issues specific to that zone,
mold portion and/or the core portion located therein. Similarly,
sacrificial material fluid heating system 202 allows for precise
temperature control of sacrificial material fluid uses for a
defined zones and/or separable mold portions to address injection
issues specific to that zone, mold portion and/or the core portion
located therein. The teachings of the disclosure can be used across
wide variety of mold materials, and mold manufacturing processes.
Fleets of molds can be created to handle wide variations in cores
and/or different components to be built. The ability to use
additive manufacturing for both mold 110, 210 and cores 112
provides significant time-savings and cost savings compared to
conventional casting processes. Further, additive manufacturing
allows for issues discovered during formation of the casting
article, e.g., core cracking, to be more quickly remedied, and also
allows for the issues to be addressed earlier in the overall
process, i.e., during the casting article formation rather than
during the investment casting process.
[0059] Embodiments of the disclosure further include mechanical
integrity premature ceramic core assessment of ceramic cores used
during the injection process and casting applications. Potential
mechanical damage (e.g., cracking, breaking, or failing) of ceramic
cores during a pour of molten metal and single crystal furnace
solidification process can be predicted. This allows, for example,
adjustment of the configuration (e.g., shape, size, etc.) of
ceramic cores very early in the investment casting process to
mitigate failure of ceramic cores during later stage molten metal
pouring.
[0060] A process is disclosed in which ceramic cores are tested at
a very early stage of an investment casting process. Instead of
performing all of the design steps up to molten metal pouring
before determining the robustness of ceramic cores, the testing
process disclosed herein uses a sacrificial fluid material to
simulate molten metal stresses on ceramic cores. The viscosity of
the sacrificial fluid material is controlled using temperature
and/or pressure to match the viscosity of the molten metal. This
saves a tremendous amount of time and money because faulty ceramic
cores are identified early in the casting process instead of after
the pouring of molten metal.
[0061] As depicted in FIG. 23, an investment casting process may
include the following: A1) Design and create a ceramic core; A2)
Create a wax pattern using the ceramic core; A3) Form a wax pattern
cluster; A4) Invest the wax cluster with a ceramic material (e.g.,
slurry, stucco) to form a mold; A5) De-wax and fire the mold (e.g.,
for strength); A6) Melt an alloy in a vacuum (or air); A7) Pour the
molten metal alloy into the mold; A8) Knock off the ceramic shell
to reveal the cast part; and A9) Perform inspection and finishing
operations on the cast part. Such an investment casting process
(e.g., A1-A9) is well within the purview of one skilled in the art
and may, of course, include fewer or additional processes.
[0062] In some cases, during the pouring of the molten alloy into a
ceramic mold (e.g., process A7), the ceramic core may break, crack,
or be damaged in some other way. This damage (YES, A10) may be
discovered, for example, during the inspection of the cast part at
process A9. When a problem with the ceramic core is identified,
changes (process A11) to the ceramic core may be required, which is
time consuming and expensive. Flow then passes back to A2, where
another wax pattern is created using the redesigned ceramic core,
and the investment casting process is again carried out using the
redesigned ceramic core. Further trial and error redesign may be
required if the new ceramic core is found to be defective (YES,
A10). Damage to the ceramic core may require a redesign of the mold
110.
[0063] According to embodiments of the disclosure, as depicted in
FIG. 23, a ceramic core may be tested very early in the investment
casting process. For example, the ceramic core may be tested
(process B1) before a corresponding wax pattern is created in A2.
If it is determined that the tested ceramic core is defective (YES,
B2), the ceramic core may be redesigned at B3 and subsequently
retested at B1. If it is determined that the ceramic core is not
defective (No, B2), flow passes to A2 and a wax pattern is created.
The testing/redesign processes (B1, B2, B3) may be repeated as
necessary until a non-defective ceramic core has been produced.
[0064] According to embodiments, the ability to manipulate the
viscosity and flow characteristics of the sacrificial material 130
fluid in one or more separable mold portions 120 of the mold 110
may be exploited to simulate molten metal stresses on one or more
portions of the ceramic core 112. This allows the ceramic core 112
to be tested very early in the investment casting process, without
actually requiring a molten metal pour.
[0065] As previously described, the mold 110 includes a plurality
of separable mold portions 120 (e.g., mold portions 120A-D, FIGS.
1-4) that are coupleable together to create the mold 110. The mold
110 is configured to form sacrificial material 130 from a
sacrificial material 130 fluid about a selected ceramic core 112.
The ceramic core 112 is positioned within the mold 110 and is
spaced from the interior surface 132 of the mold 110 such that
sacrificial material 130 fluid can readily flow between the ceramic
core 112 and the interior surface of the mold 110 to create a
casting article 102.
[0066] The viscosity of the sacrificial material 130 fluid can be
controlled to mimic the expected viscosity of the molten metal used
in the investment casting process. For example, the sacrificial
material heating system 202 (FIG. 21) may include one or more
heaters for heating the sacrificial material 130 fluid such that
the viscosity of the sacrificial material 130 fluid matches the
expected viscosity of the molten metal. The sacrificial material
heating system 202 may further include one or more pumps for
injecting the sacrificial material 130 fluid with the desired
viscosity into one or more openings or zones of the mold 110. In
the case that one or more sacrificial material inputs 284 are
included in one or more of the separable mold portions 120 of the
mold 110, the sacrificial material heating system 202 may provide
sacrificial material 130 fluid of the same viscosity or different
viscosities to one or more of the separable mold portions 120 of
the mold 110 via one or more of the sacrificial material inputs
284. Further, the temperature of each separable mold portion 120
may also be selectively regulated under control of the mold thermal
fluid controller 180 (FIGS. 20-22) by directing a temperature
controlled thermal fluid 176 therethrough. To this extent, as
described in detail for example with regard to process P3 above and
FIGS. 20-22, the viscosity of the sacrificial material 130 fluid
can be selectively controlled throughout the mold 110 by, for
example, adjusting the temperature of the sacrificial material 130
fluid (e.g., using the sacrificial material heating system 202)
and/or by adjusting the temperature of one or more of the separable
mold portions 120 (e.g., using the mold thermal fluid controller
180). A viscosity control system 300 (FIGS. 23, 24) may be provided
for controlling the sacrificial material heating system 202 and the
mold thermal fluid controller 180 to regulate the viscosity(ies) of
the sacrificial material 130 fluid used during the ceramic core 112
testing process (process B1).
[0067] The process B1 for testing the ceramic core 112 according to
embodiments is depicted in greater detail in FIG. 24. At B1-1,
viscosity data for one or more molten metal alloys at a plurality
of different temperatures is obtained. This viscosity data is
readily available and may be provided, for example, from data
sheets, from a foundry, from the source of the metal alloy, or from
any other suitable source.
[0068] At B1-2, the sacrificial material 130 fluid is heated (e.g.,
by the sacrificial material heating system 202) to a predetermined
temperature (T) at which the sacrificial material 130 fluid has a
viscosity (VISC) corresponding to the viscosity of a given molten
metal alloy. At B1-3, the core 110 is filled with the sacrificial
material 130 fluid at the viscosity (VISC) to create a wax pattern
about the ceramic core 112. At B1-4, the wax pattern is de-waxed to
reveal the underlying ceramic core 112. At B1-5, the ceramic core
112 is examined to determine if the flow of the sacrificial
material 130 fluid at the viscosity (VISC) into the mold 110 caused
any mechanical damage to the ceramic core 112. If there is damage
to the ceramic core (YES, B2), the ceramic core may be redesigned
at B3 and subsequently retested at B1. Feedback regarding any
ceramic core damage discovered during the examination process
(B1-5) may be provided to the ceramic core design team, which can
use the feedback to redesign the ceramic core to prevent such
damage.
[0069] If it is determined that the ceramic core is not defective
(NO, B2), flow passes to A2 and a wax pattern is created. The
ceramic core testing process (B1) may be repeated using sacrificial
material 130 fluid at one or more additional viscosities to
determine the effect such viscosities may have on a ceramic core
112. The same ceramic core 112, if found non defective (NO, B2),
may be retested using a sacrificial material 130 fluid at one or
more additional viscosities to determine the effect such
viscosities may have on that ceramic core 112.
[0070] In the above description of process B1 for testing the
ceramic core 112, the sacrificial material 130 fluid may have the
same viscosity throughout the mold 110. However, according to
embodiments, the viscosity of the sacrificial material 130 fluid in
one or more of the separable mold portions 120 may be adjusted
under control of the mold thermal fluid controller 180 (FIGS. 20,
21) and/or the sacrificial material heating system 202 (FIG.
21).
[0071] Referring again to FIG. 24, process B1-3 may be expanded to
include the use of a sacrificial material 130 fluid at two or more
different viscosities. This may be achieved, for example, as
described in greater detail with regard to FIGS. 20 and 21, by
adjusting the temperature of the one or more separable mold
portions 120 (process B1-3A). According to embodiments, a
temperature controlled thermal fluid 176 may be passed through the
one or more separable mold portions 120 under control of the mold
thermal fluid controller 180 to selectively adjust the temperature
of the one or more separable mold portions 120. The mold 110 is
then filled with the sacrificial material 130 fluid at a given
viscosity (or one or more different viscosities). Depending on the
temperature of each of the separable mold portions 120, the
resultant viscosity of the sacrificial material 130 fluid in each
of the separable mold portions 120 of the mold 110 may increase,
decrease, or remain the same. Advantageously, this allows the
testing of different portions of the ceramic core 112, disposed in
one or more different separable mold portions 120 of the mold 110,
using sacrificial material 130 fluid having one or more different
viscosities.
[0072] Different viscosities of sacrificial material 130 fluid may
also be provided to one or more of the separable mold portions 120
of the mold 110, as described in greater detail with regard to FIG.
21, using the sacrificial material heating system 202 (process
B1-3B). Process B1-3B may be used alone, or in combination with
process B1-3A, to vary the viscosity of the sacrificial material
130 fluid in one or more of the separable mold portions 120 of the
mold 110.
[0073] The foregoing drawings show some of the processing
associated according to several embodiments of this disclosure. In
this regard, each block within a flow diagram of the drawings
represents a process associated with embodiments of the method
described. It should also be noted that in some alternative
implementations, the acts noted in the drawings or blocks may occur
out of the order noted in the figure or, for example, may in fact
be executed substantially concurrently or in the reverse order,
depending upon the act involved. Also, one of ordinary skill in the
art will recognize that additional blocks that describe the
processing may be added.
[0074] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the disclosure. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
"Optional" or "optionally" means that the subsequently described
event or circumstance may or may not occur, and that the
description includes instances where the event occurs and instances
where it does not.
[0075] Approximating language, as used herein throughout the
specification and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about," "approximately"
and "substantially," are not to be limited to the precise value
specified. In at least some instances, the approximating language
may correspond to the precision of an instrument for measuring the
value. Here and throughout the specification and claims, range
limitations may be combined and/or interchanged, such ranges are
identified and include all the sub-ranges contained therein unless
context or language indicates otherwise. "Approximately" as applied
to a particular value of a range applies to both values, and unless
otherwise dependent on the precision of the instrument measuring
the value, may indicate +/-10% of the stated value(s).
[0076] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
disclosure has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
disclosure in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the disclosure. The
embodiment was chosen and described in order to best explain the
principles of the disclosure and the practical application, and to
enable others of ordinary skill in the art to understand the
disclosure for various embodiments with various modifications as
are suited to the particular use contemplated.
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