U.S. patent application number 14/254759 was filed with the patent office on 2014-09-25 for systems and methods for undercut features on injected patterns.
This patent application is currently assigned to COORSTEK MEDICAL LLC d/b/a IMDS, COORSTEK MEDICAL LLC d/b/a IMDS. The applicant listed for this patent is COORSTEK MEDICAL LLC d/b/a IMDS, COORSTEK MEDICAL LLC d/b/a IMDS. Invention is credited to Stephen Vander Wal.
Application Number | 20140284016 14/254759 |
Document ID | / |
Family ID | 51568257 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140284016 |
Kind Code |
A1 |
Vander Wal; Stephen |
September 25, 2014 |
Systems and Methods for Undercut Features on Injected Patterns
Abstract
A method for creating undercut features in a wax pattern in an
investment casting process is disclosed. The method comprises
designing a tooling that includes a mold for an object with an
aperture and a core corresponding in size and shape of the
aperture. Then, the mold is used to injection mold a pattern for
the object, wherein the pattern includes an opening corresponding
to the aperture. Next, a plug from the core of the tooling is
injection molded using the mold. The plug is press-fitted into the
opening of the pattern and the opening of the pattern is sealed
with the plug.
Inventors: |
Vander Wal; Stephen; (Oregon
City, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
COORSTEK MEDICAL LLC d/b/a IMDS |
Providence |
UT |
US |
|
|
Assignee: |
COORSTEK MEDICAL LLC d/b/a
IMDS
Providence
UT
|
Family ID: |
51568257 |
Appl. No.: |
14/254759 |
Filed: |
April 16, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61788444 |
Mar 15, 2013 |
|
|
|
Current U.S.
Class: |
164/45 ;
164/245 |
Current CPC
Class: |
B22C 7/02 20130101 |
Class at
Publication: |
164/45 ;
164/245 |
International
Class: |
B22C 7/02 20060101
B22C007/02 |
Claims
1. A method for creating undercut features in a wax pattern in an
investment casting process, the method comprising: designing a
tooling, wherein the tooling includes a mold for an object having
an aperture and wherein the tooling includes a core corresponding
in size and shape of the aperture; using the mold to injection mold
a pattern for the object, wherein the pattern includes an opening
corresponding to the aperture; using the mold to injection mold a
plug from the core of the tooling; press-fitting the plug into the
opening of the pattern; and sealing the opening of the pattern with
the plug.
2. The method of claim 1, wherein the wax pattern is created using
one of wax, plastic, and frozen mercury.
3. The method of claim 1, wherein the undercut feature includes at
least one of a thread, a snap feature, a blind opening, a negative
tapered feature, a locking tab, a pocket, and a hole in side
walls.
4. The method of claim 1, wherein the plug is larger than the
opening.
5. The method of claim 4, wherein the edges of the plug are 0.001''
larger than corresponding edges of the opening.
6. The method of claim 1, further comprising casting the pattern
obtained after sealing the opening of the pattern to obtain a cast
shaped like the object.
7. The method of claim 1, wherein the object is a tibial baseplate
implant.
8. A system for creating undercut features in a wax pattern, the
system comprising: a designing means to design a tooling, wherein
the tooling includes a mold for an object with an aperture, and
wherein the tooling includes a core corresponding in size and shape
of the aperture; a molding means to injection mold a pattern for
the object and a plug from the core of the tooling, wherein the
pattern includes an opening corresponding to the aperture; a means
to press-fit the plug into the opening of the pattern; and a
sealing means to seal the opening of the pattern with the plug.
9. The system of claim 8, wherein the wax pattern is created using
one of wax, plastic, and frozen mercury.
10. The system of claim 8, wherein the undercut feature includes at
least one of a thread, a snap feature, a blind opening, a negative
tapered feature, a locking tab, a pocket, and a hole in side
walls.
11. The system of claim 8, wherein the plug is larger than the
opening.
12. The system of claim 11, wherein the edges of the plug are
0.001'' larger than corresponding edges of the opening.
13. The system of claim 8, further comprising casting the pattern
obtained after sealing the opening of the pattern to obtain a cast
shaped like the object.
14. The system of claim 8, wherein the object is a tibial baseplate
implant.
15. A tool for creating undercut features in a wax pattern in
investment casting process, the tool comprising: a mold for an
object with an aperture for forming a pattern for the object,
wherein the pattern includes an opening corresponding of the
aperture; and a core corresponding in size and shape to the
aperture for forming a plug, wherein the plug is press-fit into the
opening of the pattern to seal the opening of the pattern.
16. The tool of claim 15, wherein the wax pattern is created using
one of wax, plastic, and frozen mercury.
17. The tool of claim 15, wherein the undercut feature includes at
least one of a thread, a snap feature, a blind opening, a negative
tapered feature, a locking tab, a pocket, and a hole in side
walls.
18. The tool of claim 15, wherein the plug is larger than the
opening, wherein the edges of the plug are 0.001'' larger than
corresponding edges of the opening.
19. The tool of claim 15, further comprising casting the pattern
obtained after sealing the opening of the pattern to obtain a cast
shaped like the object.
20. The tool of claim 15, wherein the object is a tibial baseplate
implant.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to and the benefit
of U.S. provisional application No. 61/788,444 filed on Mar. 15,
2013, incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present disclosure relates generally to the field of
investment casting. Specifically, this disclosure relates to
methods and systems to insert undercut features on injected
patterns.
BACKGROUND
[0003] Investment casting is an industrial process based on
lost-wax casting. Investment casting is one of the oldest known
metal-forming techniques. During World War II, the increased demand
for precisely dimensioned parts popularized the industrial use of
investment casting. The production of an investment cast results in
a ceramic casting vessel having an outer ceramic shell with an
inside surface corresponding to the desired shape, and one or more
ceramic cores positioned within the outer ceramic shell
corresponding to the desired design.
[0004] The production of investment casting involves multiple
steps. First, a master pattern is produced by a mold-maker using
one of a wax, clay, wood, plastic, steel, or another material.
[0005] Next, a mold, also known as the master die, is made from the
master pattern. The mold may be made from a low-melting-point
metal, steel, or wood. If a steel pattern was created then a
low-melting-point metal may be cast directly from the master
pattern. Alternatively, the master pattern is machined directly
into steel.
[0006] Thereafter, wax patterns are produced using the mold. The
wax pattern may be created using wax, plastic and frozen mercury.
The wax may be poured into the mold and swished around until an
even coating with a desired thickness is reached. Next, the wax
pattern is removed from the mold. Finally, the ceramic mold, known
as the investment, is produced. The ceramic mold is the cast of the
desired shape.
[0007] However, when wax patterns are produced using the mold,
often undercut features need to be included in the wax pattern. An
undercut feature of a part is one that projects back into the main
body of the part. Some examples of undercuts include threads,
certain snap features, blind openings, negative tapered features,
locking tabs, pockets, and holes in sidewalls. Undercuts add
complexity to the investment casting process. Some undercuts may
prevent the wax or plastic part from being ejected from the mold
properly. Therefore, additional methods, such as soluble wax cores
and ceramic cores, or complex, collapsing tooling are employed to
make undercut features in wax patterns. The methods using soluble
wax cores involve using a soluble wax pattern designed with
reference to an undercut feature. The soluble wax pattern is
injected using an additional wax injection tool. Further,
additional chemical processing is required to remove soluble wax.
The methods using ceramic cores involve a ceramic core pattern
designed with reference to an undercut feature. The ceramic cores
remain part of the wax pattern and are removed after the pattern is
cast.
[0008] Therefore, the methods to produce undercut features add
extra processing operations, which increase the cost from the
tooling to the casting process. Therefore, improved systems and
methods are required for creating undercut features in wax and
plastic injection molds that require fewer steps and are more
economical than the methods described above.
SUMMARY
[0009] The present disclosure relates to creating undercut features
for wax patterns used in investment casting, and instrumentation
and methods for preparation of these patterns. The primary examples
described herein illustrate how this concept is applied to creating
a tibial baseplate implant, but this concept applies equally to
other objects with undercuts, such as threads, snap features, blind
openings, negative tapered features, locking tabs, pockets, and
holes in sidewalls. The disclosed method involves designing a
tooling. The tooling includes a mold for an object with an aperture
and a core corresponding in size and shape to the aperture. The
method involves using the mold to injection mold a pattern for the
object, wherein the pattern includes an opening corresponding to
the aperture. Next, the mold is used to injection mold a plug from
the core of the tooling, press fit the plug into the opening of the
pattern, and seal the opening of the pattern with the plug.
[0010] Further, the present disclosure discloses a system for
creating undercut features in a wax pattern. The system comprises a
designing means to design a tooling, wherein the tooling includes a
mold for an object with an aperture and a core corresponding in
size and shape of the aperture. The system further comprises a
molding means to injection mold a pattern for the object and a plug
from the core of the tooling, wherein the pattern including an
opening corresponding to the aperture. In addition, the system
includes a means to press-fit the plug into the opening of the
pattern. Finally, the system includes a sealing means to seal the
opening of the pattern with the plug.
[0011] The present disclosure also discloses a tool for creating
undercut features in a wax pattern in investment casting process.
The tool comprises a mold for an object with an aperture for
forming a pattern for the object, wherein the pattern includes an
opening corresponding to the aperture. The tool further comprises a
core corresponding in size and shape to the aperture for forming a
plug, wherein the plug is press-fit into the opening of the pattern
to seal the opening of the pattern.
[0012] The disclosed method eliminates secondary manufacturing
operations and simplifies tooling design to reduce the overall
manufacturing costs associated with undercut features. Further, the
disclosed methods and systems enable better design compliance, are
repeatable and are simple as compared to earlier known methods.
[0013] Those of skill in the art will recognize that the following
description is merely illustrative of the principles of the
disclosure, which may be applied in various ways to provide many
different alternative embodiments and may be applicable outside the
fields of surgery or medical devices. While the present disclosure
is made in the context of a tibial baseplate implant for the
purposes of illustrating the concepts of the process, it is
contemplated that the present process and/or variations thereof may
be suited to other uses, such as to support other joints in the
human body and to stabilize bone fractures. Moreover, the implants,
instrumentation, and methods set forth herein may be used in open,
percutaneous, and/or minimally invasive procedures. All changes
that come within the meaning and range of equivalency of the claims
are to be embraced within their scope.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Various embodiments of the present disclosure will now be
discussed with reference to the appended drawings. It will be
appreciated that these drawings depict only typical examples of the
present disclosure and are, therefore, not to be considered
limiting of its scope.
[0015] FIG. 1A is a perspective view of a tibial baseplate implant
according to an example embodiment of present disclosure;
[0016] FIG. 1B is a top view of the tibial baseplate implant of
FIG. 1A;
[0017] FIG. 1C is a side view of the tibial baseplate implant of
FIG. 1A, with a partial cutaway to show a blind bore;
[0018] FIG. 2 is a flowchart illustrating a method for creating
undercut features in wax and plastic injection molds, according to
one aspect of the present disclosure;
[0019] FIG. 3A is a side view of a tooling for the implant of FIG.
1, with dashed lines indicating interior features;
[0020] FIG. 3B is a top down view of the tooling of FIG. 3A, with
dashed lines indicating interior features;
[0021] FIG. 3C is a cross-sectional view of the tooling of FIG. 3B,
taken along line 3C-3C in FIG. 3B;
[0022] FIG. 3D is a detail view of an area "3D" in FIG. 3C;
[0023] FIG. 3E is a detail view of an area "3E" in FIG. 3C;
[0024] FIG. 4A is a tibial baseplate pattern and two plugs created
from the tooling of FIG. 3A;
[0025] FIG. 4B is an enlarged partial cross-section of the tibial
baseplate pattern of FIG. 4A, with a plug inserted in an
opening;
[0026] FIG. 5 shows a portion of a knee with an inserted tibial
baseplate, the tibial baseplate created from the tooling of FIG.
3A, according to an example of the present disclosure;
[0027] FIG. 6A is a tooling for creating a locking tab, according
to an example embodiment of present disclosure; and
[0028] FIG. 6B is a locking tab created from the tooling of FIG.
6A.
DETAILED DESCRIPTION
[0029] While certain embodiments are shown and described in detail
below by way of illustration only, it will be clear to the person
skilled in the art upon reading and understanding this disclosure
that changes, modifications, and variations may be made and remain
within the scope of the technology described herein. Further, while
various features are grouped together in the embodiments for the
purpose of streamlining the disclosure, it is appreciated that
features from different embodiments may be combined to form
additional embodiments that are all contemplated within the scope
of the disclosed technology.
[0030] Not every feature of each embodiment is labeled in every
figure where that embodiment appears, in order to keep the figures
clear. Similar reference numbers (for example, those that are
identical except for the first numeral) may be used to indicate
similar features in different embodiments.
[0031] Any of the devices, toolings, and apparatuses described
herein may be fabricated from metals, alloys, polymers, plastics,
ceramics, waxes, woods, clays, plastics, glasses, composite
materials, or combinations thereof, including but not limited to:
PEEK, titanium, titanium alloys, commercially pure titanium grade
2, ASTM F67, Nitinol, cobalt chrome, stainless steel, UHMWPE, and
biodegradable materials, among others. Different materials may be
used within a single part. The implants disclosed herein may also
encompass a variety of surface treatments or additives to encourage
bony attachment, including but not limited to: porous coatings,
hydroxyapatite, TCP, anti-microbial additives, analgesics,
anti-inflammatories, BMP's, PMA material, bone growth promoting
material, PLLA (poly-L-lactide), PGA (polyglycolide), TCP
(tricalcium phosphate), demineralized bone, cancellous bone chips,
etc. Any implant disclosed herein may include a radiographic marker
for imaging purposes. Any implant disclosed herein may be colored,
coded, or otherwise marked to make it easier for the surgeon to
identify the type and size of the implant.
[0032] FIG. 1A shows a perspective view of a tibial baseplate
implant 100 according to an example embodiment of present
disclosure. The tibial baseplate implant 100 includes two undercut
features: a first blind bore 102 and a second blind bore 104, which
are recessed into a lower surface 106 of the tibial baseplate
implant 100. FIG. 1B is a top view of the tibial baseplate implant
100 of FIG. 1A. FIG. 1C is a side view of the tibial baseplate
implant of FIG. 1A. FIG. 1C shows additional details of the blind
bore 104 in a partial cutaway 108. The blind bore 104 is an
undercut feature circumscribing the bore. The blind bore 104 also
includes a tapered sidewall 110. The undercut angle of the tapered
sidewall 110 is illustrated by the extended dashed lines 112.
[0033] FIG. 2 is a flowchart illustrating a method 200 for creating
undercut features in wax and plastic injection molds, according to
one aspect of the present disclosure. The method 200 is explained
in the context of creating undercut features in the tibial
baseplate implant 100. FIGS. 3A-3E and 4A-4B illustrate the steps
of the method 200 for creating the blind bores 102 and 104 in the
tibial baseplate implant 100. FIG. 3A is a side view of a tooling
for the implant of FIG. 1, with dashed lines indicating interior
features. FIG. 3B is a top-down view of the tooling of FIG. 3A,
with dashed lines indicating interior features. FIG. 3C is a
cross-sectional view of the tooling of FIG. 3B, taken along the
line 3C-3C in FIG. 3B. FIG. 3D is a detailed view of an area "3D"
in FIG. 3C. FIG. 3E is a detailed view of an area "3E" in FIG. 3C.
Further, FIG. 4A depicts a tibial baseplate pattern and two plugs
created from the tooling of FIG. 4A. FIG. 4B is an enlarged partial
cross-section of the tibial baseplate pattern of FIG. 4A, with a
plug inserted in an opening.
[0034] At step 202, the method 200 involves designing a tooling.
The tooling includes a mold for an object having an aperture. The
tooling also includes a core corresponding in size and shape to the
aperture. The tooling may be made from a master pattern produced by
a mold-maker using one of a wax, clay, wood, plastic, steel, or
another material. Further, the tooling may be made using a
low-melting-point metal, steel, or wood. Moreover, the master
pattern may be machined directly into steel to produce tooling.
[0035] In an example embodiment, the object may be the tibial
baseplate implant 100 having blind bores 102 and 104. Accordingly,
a tooling 300 is created corresponding to the tibial baseplate
implant 100. The tooling 300 includes cores 302 and 304 on the side
opposite of the openings of the blind bores 102 and 104. The cores
302 and 304 corresponding in size and shape to the blind bores 102
and 104.
[0036] Next at step 204, the method 200 involves using the tooling
to injection mold a pattern for the object, such that the pattern
includes an opening corresponding to the aperture. Injection
molding involves injecting a material into a mold to produce
patterns or parts. Injection molding may be performed using metals,
glasses, elastomers, confections, and most commonly thermoplastic
and thermosetting polymers. The material for the part is fed into a
heated barrel, mixed, and forced into a mold cavity where it cools
and hardens to the configuration of the cavity.
[0037] In the example embodiment, during injection molding, the
cores 302 and 304 create the undercut surfaces corresponding to the
blind bores 102 and 104, while allowing the wax pattern to be
pulled from the tooling 300. The result is a tibial baseplate
pattern 400 with apertures 402 and 404 extending completely through
the tibial baseplate pattern 400.
[0038] At step 206, using the tooling to injection mold a plug from
the core of the tooling. Accordingly, in the example embodiment,
plugs 306 and 308 are created to fill in the apertures 402 and 404
in order to create the radius geometry on the bottom of the design.
The plugs 306 and 308 may also be referred to as inserts. A split
line 310 for the two plugs 306 and 308 occurs on the tangency of
the radius, normal to the feature opening.
[0039] At step 208, the method 200 involves press-fitting the plug
into the opening of the pattern. Referring to FIG. 4A, the tooling
300 is injected to create the tibial baseplate pattern 400 and the
two plugs 306 and 308. A partial cut away 406 shows details of the
aperture 404. FIG. 4B shows an enlarged view of the partial cut
away 406. Immediately following pattern removal, the plugs 306 and
308 are pressed into the apertures 402 and 404 on the tibial
baseplate pattern 400 until they are seated, as seen in FIG.
4B.
[0040] Finally, at step 210, the method 200 involves sealing the
opening of the pattern with the plug. Accordingly, in the example
embodiment, the plugs 306 and 308 are made slightly larger and are
press-fit into place to keep the plugs in place and create a
precise seal. For example, the plugs 306 and 308 are 0.001'' larger
than the apertures 402 and 404. The aperture 404 may be 0.474''
long while the plug 308 may be 0.475'' long. To complete the
casting process, the tibial baseplate pattern 400 with the attached
plugs 306 and 308 is cast. The finished tibial baseplate implant
100 will include the blind bores 102 and 104 with the undercut
tapered sidewalls 110.
[0041] The finished tibial baseplate implant 100 may be implanted
in a proximal tibia 502 as shown in FIG. 5. The lower surface 106
of the tibial baseplate implant 100 rests on a tibial plateau 504.
Further, pegs may be inserted in the bores 102 and 104 to secure
the tibial baseplate implant 100 in proper place in the bone.
[0042] It is appreciated that the systems and methods disclosed
herein may be used to create various patterns and objects with
blind openings, negative tapered features, undercut features such
as locking tabs, and pockets. FIG. 6A shows a tooling 600 for
creating a locking tab feature according to an exemplary embodiment
of the present disclosure. FIG. 6B is a locking tab 602 created
using the tooling 600 and the method 200 describe above.
[0043] It will be appreciated that any of the designs, methods, and
concepts contemplated herein can be mixed and matched to form
alternate embodiments. These devices and methods may be used to
create other tooling, patterns, and objects.
[0044] It should be understood that the present components,
systems, kits, apparatuses, and methods are not intended to be
limited to the particular forms disclosed. Rather, they are
intended to include all modifications, equivalents, and
alternatives falling within the scope of the claims. They are
further intended to include embodiments that may be formed by
combining features from the disclosed embodiments, and variants
thereof.
[0045] The claims are not to be interpreted as including
means-plus- or step-plus-function limitations, unless such a
limitation is explicitly recited in a given claim using the
phrase(s) "means for" or "step for," respectively.
[0046] The term "coupled" is defined as connected, although not
necessarily directly, and not necessarily mechanically.
[0047] The use of the word "a" or "an" when used in conjunction
with the term "comprising" in the claims and/or the specification
may mean "one," but it is also consistent with the meaning of "one
or more" or "at least one." The term "about" means, in general, the
stated value plus or minus 5%. The use of the term "or" in the
claims is used to mean "and/or" unless explicitly indicated to
refer to alternatives only or the alternative are mutually
exclusive, although the disclosure supports a definition that
refers to only alternatives and "and/or."
[0048] The terms "comprise" (and any form of comprise, such as
"comprises" and "comprising"), "have" (and any form of have, such
as "has" and "having"), "include" (and any form of include, such as
"includes" and "including"), and "contain" (and any form of
contain, such as "contains" and "containing") are open-ended
linking verbs. As a result, a method or device that "comprises,"
"has," "includes," or "contains," C/D one or more steps or
elements, possesses those one or more steps or elements, but is not
limited to possessing only those one or more elements. Likewise, a
step of a method or an element of a device that "comprises," "has,"
"includes," or "contains" one or more features, possesses those one
or more features, but is not limited to possessing only those one
or more features. Furthermore, a device or structure that is
configured in a certain way is configured in at least that way, but
may also be configured in ways that are not listed.
[0049] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. It is appreciated that various features of the
above-described examples can be mixed and matched to form a variety
of other alternatives. As such, the described embodiments are to be
considered in all respects only as illustrative and not
restrictive. The scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing description. All
changes that come within the meaning and range of equivalency of
the claims are to be included within their scope.
* * * * *