Grain Selector Support Cavity to Prevent Shell Gaps and Stray Grains

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Solution Overview

Problem

Ceramic rods used for supporting grain selectors in single crystal casting are prone to breakage and create gaps during the shelling process, leading to undesirable grain propagation and void formation, which compromises the integrity of the casting process.

Innovation Solution

Replace ceramic rods with a wax section that includes a passageway geometry configured to block undesirable grain propagation, using a support section in parallel with the grain selector to reinforce the shell and prevent grain intrusion into the part-forming cavity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If ceramic rods are used to support grain selectors, then strength and structural support are provided, but breakage occurs during shelling and casting leading to gaps and void formation

Engineering Contradiction:

Improvestructural support strengthVSAvoidintegrity during shelling and casting

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent changes the material parameter from ceramic to wax, fundamentally altering the mechanical properties. The wax support section is designed to be flexible and conformable during shelling, then solidifies to provide structural support, eliminating the brittleness issue of ceramic rods while maintaining necessary strength

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite structure where the wax support section integrates with the grain selector and shell material. This composite approach allows the wax to bond with surrounding materials, providing both flexibility during handling and structural integrity during casting, while eliminating the gap formation problem associated with discrete ceramic rods

Inventive Principle:

Principle #40Composite materials

2Strength

If ceramic rods are used to reinforce the shell, then load bearing capacity is improved, but gaps form between rods and shell creating pathways for competing grains

Engineering Contradiction:

Improveload bearing capacityVSAvoidgap formation and competing grain propagation

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The wax support section is designed to merge with the grain selector and surrounding shell material, creating a unified continuous structure. This eliminates the discrete rod-shell interfaces that create gaps, as the wax conforms to and bonds with adjacent surfaces, blocking pathways for competing grain propagation while maintaining load bearing capacity

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The wax support section acts as a flexible element during pattern making and shelling, conforming to the shell geometry without creating gaps. Upon solidification, it maintains intimate contact with the shell, providing reinforcement while blocking grain propagation pathways that would exist with rigid discrete rods

Inventive Principle:

Principle #30Flexible shells and thin films

Data Source

PatentEP4527519B1Casting shell with grain selector support, method of manufacturing the same, and method of using the same

Publication Date: 2026.04.22 RTX CORP

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AI summary

A casting shell (20) has: a part cavity (124) shaped for casting the part; a starter-selector cavity (60) below and connected to the part cavity (124); a connector cavity (134) between the starter-selector cavity (60) and the part cavity (124); and a support cavity (300). The support cavity (300) has: a post section (302); a first linking section (310) linking the post section (302) to a starter block section (62) of the starter-selector cavity (60); and a second linking section (312) linking the post section (302) to the connector cavity (134), the second linking section (312) having a portion descending from the post section (302) toward the connector cavity (134).