Turbine Rear Frame Machining Using Common Reference Frame

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Solution Overview

Problem

The existing manufacturing methods for turbine engine parts, such as turbine rear frames, face accuracy issues during machining due to deformations caused by assembly processes like welding, leading to misalignment and increased complexity, weight, and manufacturing costs.

Innovation Solution

A method where a first rough casting element is assembled with a second element, and both elements are machined using a common reference frame based on the second element, allowing for accurate machining and compensating for assembly deformations, ensuring precise alignment and simplifying the manufacturing process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the first element is machined after assembly using a reference frame based on the rough casting cavity walls, then the machining process is simplified, but assembly deformations cause inaccuracies in the positioning of pierced holes and misalignment with the conduit

Engineering Contradiction:

Improvemachining process simplicityVSAvoidpositioning accuracy of pierced holes

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by machining the first element before assembly rather than after. The rough casting element is machined to create precise attachment means (pierced holes, attachment lugs) while still in its pre-assembly state, ensuring that the machining reference frame is not affected by subsequent assembly deformations. This preliminary machining action resolves the contradiction by achieving high positioning accuracy before the assembly process introduces distortions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent inverts the conventional sequence by machining the first element before assembly instead of after assembly. Traditionally, the rough casting element is assembled first and then machined using the assembled structure as reference. The patent reverses this approach by machining the element in isolation using its own geometry as reference, then assembling it to the second element. This inversion eliminates the problem of assembly-induced deformations affecting machining accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If corrective solutions are implemented to compensate for machining inaccuracies, then alignment accuracy is improved, but the part becomes more complex, heavier, and more costly to manufacture

Engineering Contradiction:

Improvealignment accuracyVSAvoidpart structural complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent prevents the need for corrective solutions by performing the machining action preliminarily, before assembly. By machining the attachment means (pierced holes, attachment lugs) on the rough casting element while it is still in its undistorted pre-assembly state, the patent ensures inherent alignment accuracy without requiring additional corrective features, complex alignment mechanisms, or extra weighting. This eliminates the trade-off between accuracy and complexity.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If the first element is machined after assembly, then the rough casting cavity can serve as the reference frame, but assembly deformations cause uncertainties in the machining and require additional corrective measures

Engineering Contradiction:

Improvereference frame availabilityVSAvoidmachining accuracy reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies preliminary action by machining the first element before assembly, when the rough casting cavity walls are still intact and can reliably serve as the reference frame. By performing the machining operation at this stage, the patent ensures that the reference frame is not compromised by assembly deformations, achieving both ease of manufacture (using the cavity as reference) and reliability (maintaining machining accuracy).

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent inverts the conventional sequence by machining before assembly rather than after. This inversion allows the rough casting cavity to serve as a stable reference frame throughout the machining process without being affected by subsequent assembly operations. The inversion resolves the contradiction by ensuring that the reference frame remains reliable while maintaining manufacturing simplicity.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11692459B2Method for manufacturing a turbine engine part and the thereby produced part

Publication Date: 2023.07.04 SAFRAN AIRCRAFT ENGINES SAS

AI summary

A method for manufacturing a turbine engine part in which a first rough casting element includes a first face and a second face opposite to each other is assembled by the second face on an orifice which has a second element of the part. The method includes machining a through-cavity in the first element which opens at the first face and from the second face of the first element and machining the first face of the first element so as to form an area suitable for ensuring the attachment of a conduit on the first element. The machining of the cavity and of the first face is achieved by using a machining reference frame based on the second element.