U.S. patent application number 14/695291 was filed with the patent office on 2016-10-27 for casting with reusable precision, motion-controlled, withdrawable cores.
This patent application is currently assigned to United Technologies Corporation. The applicant listed for this patent is United Technologies Corporation. Invention is credited to Ryan C. Breneman, Steven J. Bullied, John Joseph Marcin, Dilip M. Shah, Carl R. Verner.
Application Number | 20160311016 14/695291 |
Document ID | / |
Family ID | 55794868 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160311016 |
Kind Code |
A1 |
Shah; Dilip M. ; et
al. |
October 27, 2016 |
CASTING WITH REUSABLE PRECISION, MOTION-CONTROLLED, WITHDRAWABLE
CORES
Abstract
A method of manufacturing includes providing a casting assembly,
providing a material having solid, transition, and liquid phases,
heating the material to form the liquid phase, supplying the
material to the casting assembly, cooling the material, monitoring
the solidification of the material from the liquid phase through
the transition phase, and moving one of the casting mold or the
reusable core in a first direction relative to the other when a
substantial portion of the reusable core contacts the transition
phase. The casting assembly comprises a casting mold and a reusable
core inserted within the casting mold.
Inventors: |
Shah; Dilip M.;
(Glastonbury, CT) ; Marcin; John Joseph;
(Marlborough, CT) ; Bullied; Steven J.; (Pomfret
Center, CT) ; Verner; Carl R.; (Windsor, CT) ;
Breneman; Ryan C.; (West Hartford, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Hartford |
CT |
US |
|
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
55794868 |
Appl. No.: |
14/695291 |
Filed: |
April 24, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22D 25/06 20130101;
B22D 27/045 20130101; B22D 27/06 20130101; B22C 9/101 20130101;
B22D 27/08 20130101 |
International
Class: |
B22D 25/06 20060101
B22D025/06; B22D 27/08 20060101 B22D027/08; B22D 27/04 20060101
B22D027/04 |
Claims
1. A method of manufacturing includes: providing a casting assembly
comprising: a casting mold; and a reusable core inserted within the
casting mold; providing a material that has a solidus temperature
and a liquidus temperature, wherein the material has a solid phase
at a temperature less than or equal to the solidus temperature, a
transition phase at a temperature between the solidus and liquidus
temperatures, and a liquid phase at a temperature greater than or
equal to the liquidus temperature; heating the material to form the
liquid phase; supplying the material to the casting assembly;
cooling the material; monitoring a solidification of the material
from the liquid phase through the transition phase; and moving at
least one of the casting mold and the reusable core in a first
direction relative to the other when a substantial portion of the
reusable core contacts the material in the transition phase.
2. The method of claim 1, wherein the reusable core moves relative
to the casting mold.
3. The method of claim 2 and further including: removing the
reusable core from the casting mold, wherein a viscosity of the
material surrounding the reusable core at a time immediately
preceding the removal of the core is sufficient to form one or more
hollow cavities within the material.
4. The method of claim 3 and further including: heating the casting
assembly during the removal of the core to reduce a rate of
solidification of the material.
5. The method of claim 2, wherein: the reusable core comprises: a
first structure that extends into the casting mold along a central
axis; and a second structure attached to the first structure such
that the second structure is movable relative to the first
structure in a direction substantially perpendicular to the central
axis.
6. The method of claim 5, wherein: the reusable core further
comprises: a protrusion extending from the second structure
configured to form a hollow cavity within the material, wherein a
distal end of the protrusion is tapered.
7. The method of claim 1, wherein the casting mold moves relative
to the reusable core, and wherein during the solidification of the
material, a substantial portion of the reusable core is immersed in
the transition phase.
8. The method of claim 7, wherein the casting mold moves from a
first zone having a first temperature sufficient to form the liquid
phase to a second zone having a second temperature sufficient to
form the solid phase.
9. The method of claim 7, wherein: the casting assembly further
comprises: a plate forming an end of the casting mold configured to
cool the material.
10. The method of claim 9 and further including: forming a
unidirectional crystalline structure within the material.
11. The method of claim 7 and further including: forming a passage
extending through at least a portion of the material, wherein the
passage is formed by the relative movement of the casting mold to
the reusable core.
12. The method of claim 7, wherein: the reusable core comprises: a
shaft extending in the casting mold along a central axis; a plate
having a first face affixed to the shaft and a second face opposite
the first face; and a plurality of protrusions extending from the
second face, each protrusion having a tapered distal end.
13. The method of claim 7, wherein: the reusable core comprises: a
hollow shaft extending in the casting mold along a central axis; a
plurality of spokes affixed to an outer surface of the hollow shaft
that extend outward from and generally perpendicular to the axis;
and a volute affixed to the outer surface of the hollow shaft and
the plurality of spokes, wherein the volute extends in a
circumferential direction about the axis.
14. The method of claim 7 and further including: moving the
reusable core in a second direction relative to the casting mold,
wherein the second direction is different from the first
direction.
15. The method of claim 14, wherein the second direction is
substantially perpendicular to the first direction.
16. The method of claim 15 and further including: forming a first
plurality of cavities and a second plurality of cavities within the
material, wherein the second plurality of cavities are offset from
the first plurality of cavities.
17. The method of claim 7, wherein the material is periodically
supplied to the casting assembly.
18. A method of manufacturing a die-cast component includes:
providing a casting assembly comprising: a permanent casting mold
having first and second halves that mate along mating surfaces; and
a core plate mounted relative to the permanent casting mold,
wherein the core plate defines a plurality of passages extending
therethrough; providing a material that has a solidus temperature
and a liquidus temperature, wherein the material has a solid phase
at a temperature less than or equal to the solidus temperature, a
transition phase at a temperature between the solidus and liquidus
temperatures, and a liquid phase at a temperature greater than or
equal to the liquidus temperature; heating the material to form the
liquid phase; supplying the material to the casting assembly
through the plurality of passages of the core plate; and
controlling the solidification of the material such that the core
plate is positioned substantially within the transition phase.
19. The method of claim 18 and further including: oscillating the
core plate about the axis to form porosity within the material.
Description
BACKGROUND
[0001] Conventional casting generally involves pouring liquid metal
into a sacrificial mold made from low-cost, consumable materials.
The sacrificial mold materials have melting points higher than the
liquid metal and are effectively chemically inert for the duration
of a single casting process. This casting process is regularly used
to produce low-cost, relatively simplistic parts using manual sand
casting and to produce high-cost, relatively complex aerospace
parts (e.g. blades and vanes) using lost wax investment casting.
Although the cost per mold is relatively low, the molds are
destroyed during each casting and require reproduction for
subsequent castings.
[0002] Die casting generally involves pouring liquid metal into a
durable metal mold made from two precision-machined dies. Contrary
to conventional casting processes, die casting processes aim to
rapidly mass-produce cast parts without reproducing and preparing
sacrificial molds. Commonly, this process is used to cast low
melting metals (e.g. aluminum and copper). Die casting is also used
to cast high melting alloys (e.g. nickel alloys). However, in such
processes the die life is further limited.
[0003] Contrary to conventional casting and die casting processes
in which the solidification process is largely uncontrolled (i.e.
solidification is omnidirectional), directional solidification
processes control the location and rate of solidification to form
unidirectional grain structures within the solidified metal. In its
simplest form, directional solidification of a casting is achieved
by progressively depowering heating elements, thereby cooling the
casting from one end of the mold to the other. Continuous casting
is another form of directional solidification in which liquid metal
is poured into a vertically-oriented, water-cooled copper mold.
Typically, the copper molds have a cylindrical, square or I-beam
cross section and an open-ended bottom. As liquid metal flows
through the mold, the metal along the water-cooled surfaces of the
mold solidifies and, as the remainder of the metal cools, this
process forms long, continuous billets of cast metal. In its most
advanced form, directional solidification casting is practiced in
conjunction with the investment casting process to form single
crystal cast parts. In this process, a mold full of liquid metal is
cooled from one end by a water-cooled plate. As the mold and
water-cooled plate are slowly moved from a hot zone to a cool zone
in the direction of the water-cooled plate, the liquid material
solidifies and forms columns of crystal or single crystal in the
direction of withdrawal.
[0004] In each casting process, a core can be suspended within the
mold to form a hollow cavity. However, when conventional casting or
directional investment casting processes are used, the core becomes
encapsulated in the solidified material. To remove the core and
thereby expose the hollow cavity, a chemical leaching or heating
process is used to chemically remove or burn the core. The chemical
leaching and/or baking processes destroy the core. When a die
casting process is used, the core is susceptible to damage when the
cast part is removed from the mold. Moreover, when a continuous
casting process is used, the cores are fixed and thus, the castings
are limited to fixed cross-sections. Therefore, a need exists for
an improved casting process that utilizes reusable cores to improve
manufacturing time and reduce manufacturing expense.
SUMMARY
[0005] A method of manufacturing includes providing a casting
assembly, providing a material having solid, transition, and liquid
phases, heating the material to form the liquid phase, supplying
the material to the casting assembly, cooling the material,
monitoring the solidification of the material from the liquid phase
through the transition phase, and moving one of the casting mold or
the reusable core in a first direction relative to the other when a
substantial portion of the reusable core contacts the transition
phase. The casting assembly comprises a casting mold and a reusable
core inserted within the casting mold.
[0006] A method of manufacturing a die-cast component includes
providing a casting assembly, providing a material having solid,
transition, and liquid phases, and heating the material to for the
liquid phase. The casting assembly comprises a permanent casting
mold having first and second halves that mate along a plane and a
core plate rotatably mounted relative to the permanent casting
mold. The core plate has an axis of rotation parallel to the plane
and defines a plurality of passages extending therethrough. The
method further includes supplying the material to the casting
assembly through the plurality of passages of the core plate and
controlling the solidification of the material such that the core
plate is positioned substantially within the transition phase. The
material has a solid phase when the material temperature is less
than or equal to the solidus temperature. The material has a
transition phase when the material temperature is between the
solidus and liquidus temperatures. The material has a liquid phase
when the material temperature is greater than or equal to the
liquidus temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1A is a flow chart showing a method for manufacturing a
cast component using a durable, non-wettable core coupled with
controlled movement of one or more parts of the casting
assembly.
[0008] FIG. 1B is a flow chart showing another method for
manufacturing a cast component using a durable, non-wettable core
coupled with controlled movement of one or more parts of the
casting assembly.
[0009] FIG. 2A is a schematic plan view of a durable, non-wettable
core in an extended state.
[0010] FIG. 2B is a schematic showing the casting of a component
using the core from FIG. 2A
[0011] FIG. 2C is a schematic plan view of the core from FIG. 2A in
a retracted state.
[0012] FIG. 2D is a schematic showing the creation of hollow
cavities using the durable, non-wettable, core from FIG. 2C.
[0013] FIGS. 3A and 3B are schematics showing the creation of
hollow cavities using a durable, non-wettable, core coupled with
directional solidification.
[0014] FIG. 4 is a schematic showing the creation of staggered
hollow cavities using a durable, non-wettable, core coupled with
directional solidification.
[0015] FIG. 5A is a schematic plan view of a durable, non-wettable
core having a volute supported by several spokes.
[0016] FIG. 5B is a schematic showing the creation of hollow
cavities using the core from FIG. 3A coupled with directional
solidification.
[0017] FIG. 6A is schematic showing the creation of a die-cast
component using a perforated core plate.
[0018] FIG. 6B is a schematic plan view of the core plate of FIG.
5A.
DETAILED DESCRIPTION
[0019] The present invention relates to casting apparatuses and
processes, and in particular, to casting apparatuses and processes
that couple precision movement with one or more durable,
non-wettable cores.
[0020] FIG. 1A is a flow chart showing method 10a for manufacturing
a cast component. Method 10a utilizes a durable, non-wettable core
(not shown in FIG. 1) in connection with precision movement to
create a cast component having internal hollow cavities. Forming
hollow cavities within cast components through method 10a provides
several benefits. Among those benefits are avoiding the
manufacturing cost and process time as well as the environmental
consequences associated with creating and removing sacrificial
cores from cast components through chemical leaching or baking
processes.
[0021] Generally, method 10a includes steps 12, 14, 16, 18, 20, 22,
24a, 26, and 28. Step 12 involves providing a casting assembly. The
casting assembly includes, at a minimum, a casting mold to define
the exterior features of the cast component and a durable,
non-wettable core to define the interior features (i.e. one or more
hollow cavities) of the cast component. To establish the cast
component geometry, the core is positioned relative to the casting
mold. Step 14 involves providing a material characterized by solid,
transition, and liquid phases. The boundaries between each phase
are marked by a solidus temperature and a liquidus temperature of
the material. The material takes a solid phase when the material
temperature is less than or equal to the solidus temperature and
takes a liquid phase when the material temperature is greater than
or equal to the liquidus temperature. Between the solidus and
liquidus temperatures, the material forms a transition phase
characterized by a viscous fluid relative to the material in the
liquid phase. Following step 14, the material is prepared for
casting by heating it until the material is substantially in the
liquid phase. Heating the material prior to casting is accomplished
by one or more methods well known in the art (e.g., using a
combustion or induction furnace). Once the material forms a liquid
phase, it is delivered to the casting assembly in step 18. The
material is poured into the casting assembly, thus filling at least
a portion of the casting assembly. Next, step 20 involves cooling
the material in the region adjacent the core. In particular, the
material is cooled near a portion of the core used to form internal
hollow cavities within the cast component and is not necessarily
the entire core. While the material is cooling, its material
temperature approaches the liquidus temperature. During this time,
various process parameters are monitored to evaluate the
solidification process in step 22. Among the monitored process
parameters are the material temperature in the region adjacent to
the core, the bulk material temperature, the temperature of the
casting mold, the furnace temperature, and other environmental
parameters such as ambient temperature and the like. Once the
material bounding the core enters the transition phase and the
viscosity of the material is sufficient to support the hollow
cavities within the material, one of the casting mold and the core
is held stationary while the other is moved in a direction relative
to the other in step 24a. In some embodiments, the casting mold is
heated in order to reduce a rate of solidification. If the
component is fully formed in step 26, the cast component is removed
from the casting mold in step 28. However, if the component is not
fully formed (i.e. additional hollow cavities are required), steps
18 through 24a are repeated until the cast component is fully
formed and removed in step 28. Moreover, repeating steps 18 through
24a (or alternatively 24b as described below) occurs when material
is periodically supplied to the casting assembly in order to better
control the solidification rate of the material.
[0022] Alternatively, FIG. 1B is a flow chart showing method 10b,
which is substantially similar to method 10a except method 10b
includes step 24b instead of step 24a. Step 24b involves moving the
casting mold in a first direction relative to the core and moving
the core in a second direction relative to the casting mold, the
first direction being different than the second direction.
Combining the motion of the casting mold and core allows method 10b
to be applied to directional solidification processes. In one
embodiment, movement of the casting mold controls the rate and
direction of solidification by moving the casting mold from a
melting zone (i.e. a furnace) to a solidification zone (i.e. a
cooler region adjacent to the furnace). In such an embodiment, the
movement of the core controls the formation of hollow cavities
within the cast component during the solidification process.
[0023] For the core to be successfully implemented in methods 10a
and 10b, the core is designed to withstand multiple casting cycles
without replacement. A core withstanding only a few casting cycles
is sufficiently durable if the manufacturing costs (e.g., material
cost, manufacturing time, labor) are reduced by eliminating
chemical leaching and/or baking steps associated with sacrificial
cores. To attain core durability, the core is constructed from one
or more materials that produce a non-wettable surface (i.e. a
surface that inhibits the ability of a liquid to wet or cover the
surface). Additionally, the core material has thermal shock
resistance and erosion resistance sufficient to enable the core to
survive multiple casting cycles that produce cast components within
manufacturing tolerances. For example, melting metals such as tin,
zinc, copper, and aluminum as well as the alloys associated with
such materials requires core materials with lower temperature
resistance than the core materials used for melting iron and nickel
base alloys. In some embodiments, the core is constructed from
silicide or ternary intermetallic metals (e.g., MAX phase
materials) with appropriate ceramic coatings for casting higher
temperature materials such as iron and nickel base alloys.
Typically, ceramic coatings include alumina and yittra-stabilized
zirconia based coatings. In other embodiments used for
manufacturing relatively thin cast components, thin metallic sheets
with thermal barrier and/or environmental coatings are used to
create thin cast components that are not achievable with brittle
materials.
[0024] Movement of the core and/or the casting mold is a repeated
motion or pattern of motion used to define the desired shape of the
cast component. Depending on the motion of the core and/or casting
mold, voids, porosity, foam structures, and lattice structures are
created. Such motion can be controlled remotely or with embedded
digital motors and/or actuators.
[0025] Typically, the casting material is a metal (e.g., aluminum,
carbon steel, and nickel and associated alloys). However, methods
10a and 10b can be applied to other materials such as organic and
inorganic salts, paraffin wax, plastics, or food items such as
confectionary sugar syrup or gelatins. When such nonmetal materials
are used, the resulting cast component (i.e. foam, lattice, cored
material) can be used for cosmetic reasons.
[0026] As will be appreciated by those skilled in the art, methods
10a and/or 10b apply to conventional casting, die-casting, and
directional solidification casting processes as will be described
in greater detail below. Although the following casting molds and
cores will be described in the following embodiments with a
particular geometry, it is understood that other geometries can be
implemented so long as the geometries are compatible with methods
10a and/or 10b as described generally above.
[0027] FIG. 2A is a schematic plan view of durable, non-wettable
core 30 shown in an extended state. Core 30 includes structures 32,
34, and 36. Structure 32 extends along axis 33, which intersects
the geometric center of structure 32. Structure 34 has one or more
protrusions 34a, and structure 36 has one or more protrusions 36a
for forming hollow cavities within a cast component (not shown in
FIG. 2A). Structures 34 and 36 are attached to structure 32 in a
manner that allows structures 34 and 36 to move or retract relative
to structure 32. As such, structure 32 is generally disposed
between structures 34 and 36. In some embodiments, structures 34
and 36 are attached to opposing faces of structure 32.
[0028] FIG. 2B is a schematic showing the casting of a component
using core 30 from FIG. 2A in a conventional casting process. Core
30 includes structures 32, 34, and 36 having axis 33 and
protrusions 34a and 36a as discussed above. To cast a component
using a conventional casting process, core 30 is assembled within
casting assembly 38 which also includes casting mold 40. Core 30,
configured in an extended position, is positioned relative to mold
40. In some embodiments, core 30 is inserted within mold 40 such
that axis 33 of structure 32 intersects a geometric center of mold
40. However, in other embodiments, core 30 is positioned at an
angle relative to mold 40 and/or offset from the geometric center
of mold 40 as necessary to produce a cast component having the
desired geometry.
[0029] To form a cast component, material 42 is melted and poured
into casting assembly 38 in accordance with method 10a. After
material 42 conforms to the surfaces of core 30 and mold 40,
casting assembly 38 is placed in a cooling environment.
Omnidirectional heat loss from material 42 through casting assembly
38 causes material 42, initially in a liquid phase, to form a
transition phase. Portions of material 42 adjacent to mold 40 but
that is not contacting mold 30 can solidify. When the remaining
portions of material 42 adjacent to core 30 are relatively viscous
(i.e., form transition phase), core 30 is removed.
[0030] Prior to removal, structures 34 and 36 are retracted
relative to structure 32 of core 30 as depicted in FIG. 2C. In some
embodiments, structure 34 slides along a mating face of structure
32 in a direction indicated by arrow 44 towards and generally
perpendicular to axis 33 while structure 36 moves in an opposing
direction along another mating face of structure 32 as indicated by
arrow 46. Thus, core 30 takes a retracted form that allows core 30
to be removed from casting assembly 38.
[0031] FIG. 2D is a schematic showing the creation of hollow
cavities 50 and 52 by withdrawing core 30 in a withdrawal direction
indicated by arrow 48 from casting assembly 38. As can be seen in
FIG. 2D, the retracted state of core 30 permits structures 32, 34,
and 36 to be withdrawn from casting assembly 38 without interfering
with solidifying material 42. In some embodiments, protrusions 36a
and 34a (not shown in FIG. 2D) have a triangular cross-section as
shown in FIG. 2D and form similarly-shaped hollow cavities 50 and
52, respectively. However, other protruding shapes are possible so
long as the viscosity of material 42 adjacent to core 30
immediately prior to withdrawal is sufficient to support the
internal features (e.g., hollow cavities 50 and 52) once core 30 is
removed. The required viscosity of material 42 depends on the size
of the internal feature to be formed and the properties and
temperature of material 42 when core 30 is withdrawn from material
42.
[0032] FIGS. 3A and 3B are schematics of casting assembly 54
showing the creation of hollow cavities 56 (see FIG. 3B) using
durable, non-wettable, core 58 coupled with directional
solidification. Core 58 includes shaft 60, plate 62, and at least
one protrusion 64. Shaft 60 extends along axis 66, which intersects
the geometric center of shaft 60. Shaft 60 has opposing ends 68 and
70. Plate 62 is attached to shaft 60 at end 70 and has at least one
protrusion 64 extending therefrom in a direction opposite shaft 60.
In some embodiments, core 58 has a plurality of protrusions 64
extending from plate 62, being spaced along plate 62 so as to form
a comb-like shape. To form casting assembly 54, core 58 is
positioned relative to casting mold 72. Casting mold 72 includes
side mold 74 that encircles core 58 and chill plate 76 disposed at
an end of casting mold 72 abutting and/or attached to side mold
74.
[0033] To form a cast component, material 78 is supplied to casting
assembly 54. In some embodiments, material 78 fills the interior
volume of casting assembly 54 defined by casting mold 72 and core
58. In other embodiments, material 78 is fed to casting assembly 54
at an average feed rate. In such embodiments, the feed rate can be
characterized by periodically supplying material 78 to casting
assembly 54 to better control the solidification of material 78 in
casting assembly 54.
[0034] Chill plate 76 is configured to cool material 78 to promote
solidification of material 78 while side mold 74 is insulated
and/or heated to prevent premature solidification of material 78.
In some embodiments, chill plate 76 is a water-cooled metal plate
(e.g., a water-cooled copper plate). This arrangement of casting
mold 72 causes material 78 to solidify adjacent to chill plate 76
while material 78 remains in a liquid or transition phase elsewhere
within casting mold 72. Thus, material 78 forms solid phase 78a,
transition phase 78b, and liquid phase 78c, in sequential order,
extending from a region adjacent chill plate 76.
[0035] Referring now to FIG. 3B, casting mold 72 is moved relative
to core 58 when material 78 within transition phase 78b has a
viscosity sufficient to form hollow cavities 56. Solid phase 78a
and transition phase 78b grow to encompass a substantial portion of
protrusions 64 of core 58. Because solid phase 78a generally causes
material 78 to contract, distal ends of protrusions 64 (i.e. and
end opposite plate 62) are tapered in some embodiments to
counteract this contraction and promote relative movement of
casting mold 72 relative to core 58. Furthermore, casting mold 72
is moved in a direction indicated by arrow 80, which is generally
parallel to axis 66 of core 58. To further promote solidification
of material 78, casting mold 72 is typically moved from a melting
region to a solidification region. The melting region (e.g., the
interior of a furnace) has a temperature sufficient to maintain
material 78 in liquid phase 78c while the solidification region
(e.g., the exterior of a furnace), has a temperature sufficient to
maintain material 78 in solid phase 78a. Thus, the solidification
of material 78 promotes directional grain structures in solid phase
78a and hollow cavities 56 are formed without using chemical
leaching or baking processes to remove core 58.
[0036] FIG. 4 is a schematic showing the creation of staggered
hollow cavities 81a and 81b using casting assembly 54 as previously
described above. However, instead of restraining core 58 and moving
casting mold 72 to form hollow cavities 56 (see FIG. 3B), core 58
is moved in directions indicated by bi-direction arrow 83a and/or
bi-directional arrow 83b. In some embodiments, core 58 is moved in
a direction that is perpendicular to the withdrawal direction of
casting mold 72 indicated by arrow 80. Thus, by moving both casting
mold 72 and core 58, hollow cavities 81a and 81b are formed in a
staggered pattern. The sizes of hollow cavities 81a and 81b are
determined by the rate at which core 58 and casting mold 72 are
moving relative to one another.
[0037] FIGS. 5A and 5B are schematic views of casting assembly 82
showing the creation of hollow cavities 84 using durable,
non-wettable core 86. Casting assembly 82 includes core 86 and
casting mold 87. Core 86 includes hollow shaft 88 and spokes 90
supporting volute 92. Hollow shaft 88 extends along axis 94, which
intersects a geometric center of core 86, and has opposing ends 96
and 98 (see FIG. 5B). Spokes 90 extend from end 96 of hollow shaft
88 in an outward and generally perpendicular direction relative to
axis 94. Casting mold 87 includes side mold 100 and chill plate
102, each being substantially similar to side mold 74 and chill
plate 76.
[0038] To form a cast component, material 104 is supplied to
casting assembly 82. In some embodiments, material 104 fills the
interior volume of casting assembly 82 defined by casting mold 87
and core 86. In other embodiments, material 104 is fed to casting
assembly 82 at an average feed rate. In such embodiments, the feed
rate can be characterized by periodically supplying material 104 to
casting assembly 82 to better control the solidification of
material 104 in casting assembly 82. Material 104 forms solid phase
104a, transition phase 104b, and liquid phase 104c as a result of
chill plate 102 cooling material 104 from an end of casting mold
87. In any embodiment, spokes 90 are shaped (e.g., tapered) such
that material 104 readily flows along spokes 90 and through volute
92.
[0039] In a process similar to the directional casting process
described in FIGS. 3A and 3B, FIG. 5B shows casting mold 87 moving
relative to core 86. Casting mold 87 movement occurs when material
104 within transition phase 104b has a viscosity sufficient to form
hollow cavities 84. Continued cooling of material 104 by chill
plate 102 causes solid phase 104a and transition phase 104b to grow
until phases 104a and 104b encompass a substantial portion of
volute 92. Because solid phase 104a generally causes material 104
to contract, edges of volute 92 facing chill plate 102 are tapered
in some embodiments to counteract this contraction and promote
relative movement of casting mold 87 relative to core 86. In some
embodiments, casting mold 87 is moved in a direction indicated by
arrow 106, which is generally parallel to axis 94 of core 86. To
further promote solidification of material 104, casting mold 87 is
typically moved from a melting region to a solidification region.
The melting region (e.g., the interior of a furnace) has a
temperature sufficient to maintain material 104 in liquid phase
104c while the solidification region (e.g., the exterior of a
furnace), has a temperature sufficient to maintain material 104 in
solid phase 104a. Thus, the solidification of material 104 promotes
directional grain structures in solid phase 104a and hollow
cavities 84 are formed without using chemical leaching or baking
processes to remove core 86. The end result of this process is to
cast a spiral roll of sheet metal without using a consumable core.
In a directional solidification process this will allow casting of
long single crystal sheet metal, not attainable by solidification
furnaces currently available.
[0040] FIG. 6A is schematic of casting assembly 108 showing the
creation of a die-cast component using perforated core plate 110
and casting mold 112. Casting assembly 108 includes core plate 110,
casting mold 112, material inlet 114, and shot tube 116. Core plate
110 is disposed between casting mold 112 and shot tube 116. To form
a cast component, material 118 is fed through inlet 114 into shot
tube 116. Piston 120 includes shaft 122 and head 124. Actuating
piston 120 along shot tube 116 in a direction towards core plate
110 forces material 118 through core plate 110 into casting mold
112. As material 118 is fed through core plate 110, casting mold
112 is moved parallel to core plate 110 as indicated by
bi-directional arrow 126. Thus, an oscillating casting mold 112
creates porosity within material 118, which has a transition phase
as it flows through core plate 110 and solidifies within casting
mold 112. The porosity within material 118 increases as the
oscillating motion of casting mold 112 increases. Conversely, the
porosity within material 118 decreases as the oscillating motion of
casting mold 112 decreases. To facilitate removal of the cast
component (not shown in FIG. 6A), casting mold 112 is split in at
least two halves 128a and 128b that have mating surfaces. In some
embodiments, halves 128a and 128b mate along a common plane.
Internal surfaces 130a and 130b of each mold half 128a and 128b,
respectively, define the exterior surfaces of a cast component (not
shown in FIG. 6A).
[0041] FIG. 6B is a schematic plan view of core plate 110 of FIG.
6A. When viewed as shown in FIG. 6B, core plate 110 has a
cross-section that conforms to shot tube 116. Core plate 110
includes at least one passage 132 through which material 118
traverses core plate 110 from shot tube 116 to casting mold 112. In
some embodiments, core plate 110 includes a plurality of passages
132, although multiple passages 132 are not required.
Discussion of Possible Embodiments
[0042] The following are non-exclusive descriptions of possible
embodiments of the present invention.
[0043] A method of manufacturing includes providing a casting
assembly, providing a material having solid, transition, and liquid
phases, heating the material to form the liquid phase, supplying
the material to the casting assembly, cooling the material,
monitoring the solidification of the material from the liquid phase
through the transition phase, and moving one of the casting mold or
the reusable core in a first direction relative to the other when a
substantial portion of the reusable core contacts the transition
phase. The casting assembly comprises a casting mold and a reusable
core inserted within the casting mold. The material has a solid
phase at a temperature less than or equal to the solidus
temperature. The material has a transition phase at a temperature
between the solidus and liquidus temperatures. The material has a
liquid phase at a temperature greater than or equal to the liquidus
temperature.
[0044] The method of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components:
[0045] A further embodiment of the foregoing method, wherein the
reusable core can move relative to the casting mold.
[0046] A further embodiment of any of the foregoing methods can
further include removing the reusable core from the casting mold.
The viscosity of the material adjacent to the reusable core at a
time immediately preceding the removal of the core can be
sufficient to form one or more hollow cavities within the
material.
[0047] A further embodiment of any of the foregoing methods can
further include heating the casting assembly during the removal of
the core to reduce a rate of solidification of the material.
[0048] A further embodiment of any of the foregoing methods,
wherein the reusable core can further comprise a first structure
that extends into the casting mold along a central axis and a
second structure attached to the first structure such that the
second structure is movable relative to the first structure in a
direction substantially perpendicular to the central axis.
[0049] A further embodiment of any of the foregoing methods,
wherein the reusable core can further comprise a protrusion
extending from the second structure configured to form a hollow
cavity within the material, wherein a distal end of the protrusion
can be tapered.
[0050] A further embodiment of any of the foregoing methods wherein
the casting mold can move relative to the reusable core, and
wherein during the solidification of the material, a substantial
portion of the reusable core can be immersed in the transition
phase.
[0051] A further embodiment of any of the foregoing methods,
wherein the casting mold can move from a first zone having a first
temperature sufficient to form the liquid phase to a second zone
having a second temperature sufficient to form a solid phase.
[0052] A further embodiment of any of the foregoing methods,
wherein the casting assembly can further comprise a plate forming
an end of the casting mold configured to cool the material.
[0053] A further embodiment of any of the foregoing methods can
further include forming a unidirectional crystalline structure
within the material.
[0054] A further embodiment of any of the foregoing methods can
further include forming a passage extending through at least a
portion of the material, wherein the passage can be formed by the
relative movement of the casting mold to the reusable core.
[0055] A further embodiment of any of the foregoing methods,
wherein the reusable core can comprise a shaft extending in the
casting mold along a central axis, a plate having a first face
affixed to the shaft and a second face opposite the first face, and
a plurality of protrusions extending from the second face, each
protrusion having a tapered distal end.
[0056] A further embodiment of any of the foregoing methods,
wherein the reusable core can comprise a hollow shaft extending in
the casting mold along a central axis, a plurality of spokes
affixed to an outer surface of the hollow shaft that extend outward
from and generally perpendicular to the axis, and a volute affixed
to the outer surface of the hollow shaft and the plurality of
spokes, wherein the volute extends in a circumferential direction
about the axis.
[0057] A further embodiment of any of the foregoing methods can
further include moving the reusable core in a second direction
relative to the casting mold, wherein the second direction is
different from the first direction.
[0058] A further embodiment of any of the foregoing methods,
wherein the second direction can be substantially perpendicular to
the first direction.
[0059] A further embodiment of any of the foregoing methods can
further include forming a first plurality of cavities and a second
plurality of cavities within the material, wherein the second
plurality of cavities can be offset from the first plurality of
cavities.
[0060] A further embodiment of any of the foregoing methods,
wherein the material can be periodically supplied to the casting
assembly.
[0061] A method of manufacturing a die-cast component includes
providing a casting assembly, providing a material having solid,
transition, and liquid phases, and heating the material to for the
liquid phase. The casting assembly comprises a permanent casting
mold having first and second halves that mate along a plane and a
core plate rotatably mounted relative to the permanent casting
mold. The core plate has an axis of rotation parallel to the plane
and defines a plurality of passages extending therethrough. The
method further includes supplying the material to the casting
assembly through the plurality of passages of the core plate and
controlling the solidification of the material such that the core
plate is positioned substantially within the transition phase. The
material has a solid phase at a temperature less than or equal to
the solidus temperature. The material has a transition phase at a
temperature between the solidus and liquidus temperatures. The
material has a liquid phase at a temperature greater than or equal
to the liquidus temperature.
[0062] The method of the preceding paragraph can optionally
include, additionally and/or alternatively, any one or more of the
following features, configurations and/or additional
components:
[0063] A further embodiment of any of the foregoing methods can
further include oscillating the core plate about the axis to form
porosity within the material.
[0064] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *