INVESTMENT CASTING UTILIZING FLEXIBLE WAX PATTERN TOOL
An investment casting process wherein the wax pattern tool ( 44 ) is flexible to facilitate removal of the tool from the cast wax pattern ( 52 ) even when the cast shape would otherwise require multiple pull planes. The flexible tool may include a flexible insert ( 42 ) precisely indexed to a surrounding coffin mold ( 40 ), and thereby to an enclosed ceramic core ( 10 ). Positioning pins ( 106 ) may extend from the flexible tool to make compliant contact against the core prior to a wax injection step. The surface of the resulting wax pattern may contain an engineered topography ( 36 ) replicated through the flexible surface from a master tool ( 12 ). The flexible tool may encase thermally conductive or magnetic particles ( 92 ), or other active device ( 96 ) such as a sensor or vibrator which is operable during wax injection.
1 . A tool for forming a wax pattern as part of an investment casting process, the tool comprising:
a coffin mold;
a core disposed within and supported in position relative to the coffin mold; and
a flexible liner comprising a feature to be replicated in wax during a wax injection step of the investment casting process, the liner indexed to the coffin mold so as to position the feature at a known location relative to the core during the wax injection step.
2 . The tool of claim 1 , wherein the feature comprises a flexible positioning element formed integral to the flexible liner and making contact with the core to support the core during the wax injection step.
3 . The tool of claim 1 , wherein the feature comprises an insert comprising a non-linear leg which extends to make contact with the core.
4 . The tool of claim 3 , wherein the insert comprises a leg which extends to make contact with the core to support the core during the wax injection step.
5 . The tool of claim 1 , wherein the feature comprises a pin which extends to make contact with the core to support the core during the wax injection step.
6 . The tool of claim 5 , further comprising:
a recess formed in an inner surface of the flexible liner;
a supporting element disposed within the recess; and
the pin passing through an opening in the supporting element and extending toward the core.
7 . A tool for forming a wax pattern as part of an investment casting process, the tool comprising:
a tool body comprising a flexible inner surface defining a desired outer surface geometry of the wax pattern;
a core disposed within the tool body, the core forming part of the wax pattern after a wax injection step; and
a positioning element disposed between the core and the tool body and supported by the flexible inner surface to provide compliant support for the core during the wax injection step.
8 . The tool of claim 7 , wherein the positioning element is formed integral with the flexible inner surface of the tool body.
9 . The tool of claim 7 , wherein the positioning element is affixed to the flexible inner surface of the tool body with an adhesive.
10 . The tool of claim 7 , further comprising:
a recess formed in the flexible inner surface of the tool body; and
the positioning element disposed within the recess and extending beyond the flexible inner surface toward the core.
11 . The tool of claim 7 , wherein the positioning element comprises a spacer that can be pulled out of the wax pattern prior to a subsequent ceramic shelling step or that will burn out during a subsequent ceramic shell hardening step.
12 . The tool of claim 7 , wherein the positioning element comprises a ceramic material that will remain entrapped by the wax pattern after the wax injection step and will then become integral with a subsequently applied ceramic shell material.
13 . The tool of claim 7 , wherein the positioning element further comprises:
a supporting element disposed within a recess formed in the flexible inner surface of the tool body; and
a pin passing through an opening in the supporting element and extending toward the core.
14 . The tool of claim 7 , wherein the tool body comprises:
a coffin mold; and
a flexible insert comprising the flexible inner surface disposed within the coffin mold; and
cooperating indexing features formed on the coffin mold and the flexible insert for positioning the flexible insert within the coffin mold at a known relative location.
15 . The tool of claim 7 , wherein the tool body comprises:
a coffin mold; and
a flexible insert comprising the flexible inner surface disposed within the coffin mold; and further comprising:
a reactive element disposed within the flexible member.
16 . The tool of claim 15 , wherein the reactive element comprises one of the group consisting of a sensor, an actuator, a temperature control element, a magnet, particles reactive to magnetic energy, and particles exhibiting a coefficient of thermal conductivity different than a coefficient of thermal conductivity of flexible material of the flexible member surrounding the particles.
17 . The tool of claim 7 , wherein the tool body comprises:
a coffin mold;
a flexible insert defining the flexible inner surface disposed within the coffin mold; and
a precision ceramic insert disposed in a recess of the flexible inner surface.
18 . A tool for forming a wax pattern as part of an investment casting process, the tool comprising:
a tool body comprising a flexible member defining a desired outer surface geometry of the wax pattern;
a core disposed within the tool body, the core forming part of the wax pattern after a wax injection step;
a means for supporting the core within the tool body; and
a reactive element disposed within the flexible member.
19 . The tool of claim 18 , wherein the reactive element comprises one of the group consisting of a sensor, an actuator, a temperature control element, a magnet, particles reactive to magnetic energy, and particles exhibiting a coefficient of thermal conductivity different than a coefficient of thermal conductivity of flexible material of the flexible member surrounding the particles.
20 . The tool of claim 18 , wherein the means for supporting the core within the tool body comprises a positioning element disposed between the core and the tool body and supported by the flexible member to provide compliant support for the core during the wax injection step.
21 . The tool of claim 18 , wherein the means for supporting the core within the tool body further comprises:
a supporting element disposed within a recess formed in the flexible member of the tool body; and
a pin passing through an opening in the supporting element and extending toward the core.
22 . An investment casting method wherein the improvement comprises:
positioning a ceramic core within a wax injection mold comprising a flexible member having an inner surface defining a desired outer surface geometry of a wax pattern to be formed within the mold; and
supporting the ceramic core from the flexible member while injecting wax into the wax injection mold around the ceramic core to form the wax pattern.
23 . The method of claim 22 , further comprising forming the flexible member to comprise a protrusion extending away from the inner surface toward the core for contacting the core to provide support to the core during the step of injecting wax.
24 . The method of claim 23 , further comprising forming the protrusion to be integral with the flexible member inner surface.
25 . The method of claim 22 , further comprising:
forming a recess in the flexible member inner surface; and
inserting a spacer into the recess to extend toward the core for contacting the core to provide support to the core during the step of injecting wax; and
removing the spacer after the step of injecting wax.
26 . The method of claim 22 , further comprising:
forming a recess in the flexible member inner surface;
inserting a ceramic insert into the recess to extend toward the core for contacting the core to provide support to the core during the step of injecting wax;
allowing the injected wax to solidify to form the wax pattern within the wax injection mold;
removing the wax injection mold while retaining the ceramic insert with the wax pattern; and
forming a ceramic shell structure including the ceramic insert around the wax pattern.
27 . The method of claim 22 , further comprising:
forming a recess in the flexible member inner surface;
inserting a supporting element comprising an opening into the recess;
inserting a pin into the opening to extend toward the core for contacting the core to provide support to the core during the step of injecting wax;
allowing the injected wax to solidify to form the wax pattern within the wax injection mold;
removing the wax injection mold from the wax pattern and removing the supporting element from the pin while retaining the pin in the wax pattern, a portion of the pin then extending away from the core beyond the wax pattern; and
forming a ceramic shell structure around the wax pattern and encompassing the extending portion of the pin.
28 . The method of claim 22 , wherein the inner surface defines an engineered surface topography for the outer surface geometry.
29 . The method of claim 22 , further comprising:
prior to injecting wax, affixing an insert to the flexible member inner surface, the insert comprising an engineered topography on its surface proximate the core;
removing the flexible member from the wax pattern after injecting wax while retaining the insert in the wax; and
coating the wax pattern and insert with ceramic material to form a ceramic casting vessel.