Investment casting utilizing flexible wax pattern tool for supporting a ceramic core along its length during wax injection

Abstract

An investment casting process wherein the wax pattern tool (42) is flexible to provide compliant support for an enclosed ceramic core (10) and to facilitate removal of the tool from the cast wax pattern (52) even when the cast shape would otherwise require multiple pull planes. Positioning pins (106) may extend from the flexible tool to make compliant contact against the core during the wax injection step. The pins may cooperate with a pedestal (128) formed on the core to support the core along multiple axes during wax injection, thereby allowing a higher wax injection pressure without damage to the core.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of co-pending application Ser. No. 12 / 961,740 filed 7 Dec. 2010 (attorney docket 2010P13199US), which in turn claimed benefit of the 8 Dec. 2009 filing date of U.S. provisional application No. 61 / 267,519 (attorney docket 2009P22785US).FIELD OF THE INVENTION[0002]This invention relates generally to the field of investment casting, and more particularly, to using a flexible tool or mold to form a wax pattern as part of an investment casting process.BACKGROUND OF THE INVENTION[0003]Investment casting is one of the oldest known metal-forming processes, dating back thousands of years to when it was first used to produce detailed artwork from metals such as copper, bronze and gold. Industrial investment castings became more common in the 1940's when World War II increased the demand for precisely dimensioned parts formed of specialized metal alloys. Today, investment casting is commonly used in the aer...

AI Technical Summary

Benefits of technology

[0008]The present invention is part of an entirely new regiment for investment casting, and it focuses on the use of a flexible tool when casting a wax pattern around a ceramic core. In particular, the ceramic core is supported from the flexible tool at points along its length during the wax injection step. The present invention allows higher pressures to be used for wax injection while reducing the incidence of damage or movement of the core during the wax injection step. The overall investment casting process is described herein so that the reader may appreciate how the present invention fits within and contributes to the new regiment.

[0009]A flexible wax pattern mold may be formed as a hybrid tool having a flexible insert within a coffin mold. The flexible insert facilitates the removal of the wax pattern tool from the cast wax pattern by deforming the flexible insert around cast features that would otherwise require multiple pull planes for hard tooling. The flexible insert may be cast from a master tool that is machined from a relatively low cost, low hardness material such as aluminum or mild steel.

Problems solved by technology

Some desired surface topographies are so fine that they may not survive in the surface of the wax during subsequent handling and ceramic shell forming steps.

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