Threaded Hole Repair With Continuous Threads in Cast Engine Parts

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Solution Overview

Problem

Casting defects in gas turbine engine components, such as compressor or turbine casings and gearbox housings, often go undetected until after machining, leading to costly scrapage due to the presence of defects like misruns, cold shuts, or shrinkage defects around threaded holes.

Innovation Solution

A method involving the installation of a modified tap inside a threaded hole with existing threads, followed by the addition of repair material to cover the defect and form new threads that are continuous with the existing ones, allowing for the repair of defective regions without scrapping the entire part.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a casting part with defects is scrapped, then the reliability of the final product is ensured, but the loss of expensive parts and materials increases

Engineering Contradiction:

Improveproduct reliabilityVSAvoidloss of expensive casting parts

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

Instead of discarding the entire casting part when a defect is detected, the invention recovers the valuable part by removing only the defective region containing the defect and forming a new threaded hole in the recovered portion, thereby salvaging the expensive casting while eliminating the defect

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The invention segments the problem by separating the defective region from the rest of the valuable casting part. By removing only the minimal portion containing the defect and creating a new threaded hole, the sound portion of the casting is preserved and reused

Inventive Principle:

Principle #1Segmentation

2Object-affected harmful factors

If the entire casting is scrapped due to detected defects, then the harmful defects are eliminated, but the manufacturing cost increases

Engineering Contradiction:

Improvedefects in castingVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSLoss of energy

Solution Approach 1:

The invention extracts and removes only the defective region from the casting rather than discarding the entire part. By taking out the minimal portion containing the defect and forming a new threaded hole in the recovered portion, the harmful defect is eliminated while preserving the valuable casting and reducing manufacturing cost

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If material is added to cover defects around threaded holes, then the defects are covered, but the thread continuity must be maintained

Engineering Contradiction:

Improvedefect coverageVSAvoidthread continuity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention performs preliminary action by forming the new threaded hole through the added material and into the base material before final assembly. This ensures that the threads are properly formed and continuous from the beginning, rather than attempting to repair threads after defect coverage

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The added material acts as an intermediary that bridges the defect region and the base material. By forming a new threaded hole through this intermediary material, continuous threads are achieved that connect the added material to the underlying base material, ensuring both defect coverage and thread continuity

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11559845B2Method of repairing a region of a part including a threaded hole

Publication Date: 2023.01.24 PRATT & WHITNEY CANADA CORP

AI summary

Methods of repairing a periphery of a threaded hole of a part are provided. An embodiment of the method includes adding material to a region of the part including on a periphery of the threaded hole. New threads are formed in the added material. The new threads are continuous with existing threads formed in the hole.