INVESTMENT CASTING UTILIZING FLEXIBLE WAX PATTERN TOOL

• US 20110132564A1
• Filed: 12/07/2010
• Published: 06/09/2011
• Est. Priority Date: 12/08/2009
• Status: Abandoned Application

• Current Assignee: Mikro Systems, Inc., Siemens AG
• Original Assignee: Siemens AG
• Inventors: Heneveld, Benjamin E., Sheehan, Kevin C., James, Allister W., Fraser, Iain A., Burns, Andrew J., Merrill, Gary B.
• Application Number:
  US12/961,740
• Publication Number:
  US 20110132564A1
• Time in Patent Office: Days
• US Class Current: 164/30
• CPC Class Codes: B22C 7/02 Lost patterns
• CPC Class Codes: B22C 7/06 Core boxes
• CPC Class Codes: B22C 9/04 Use of lost patterns
• CPC Class Codes: B22C 9/10 Cores; Manufacture or installation of cores breaker cores B22C9/084
• CPC Class Codes: B22C 9/101 Permanent cores
• CPC Class Codes: B22C 9/103 Multipart cores
• CPC Class Codes: B22C 9/24 for hollow articles

Abstract

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.

Claims

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.