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Adaptive Control of Manufacturing Processes for a New Generation of Jet Engine Components

State of the Art - Background

Tags: Air

The manufacture of safety-critical rotating components in modern aero engines is by nature very conservative. To achieve the required engine performance, thermal and mechanical stresses are pushed to the maximum, which in turn leaves the choice of materials with exotic super alloys. These materials are classed as difficult to machine under normal circumstances, but when added to the changes in mechanical properties, machining processes can never be fully optimised. Stringent legislative controls are placed on safety critical component manufacture to ensure that parts entering service will function correctly and safely to a declared service life, and in declaring the service life for such a part, the machinability issues stated above have to be taken into consideration. Hence manufacturing process parameters are often reduced or tools are changed early to ensure part surface integrity. The industry method adopted is to then 'freeze' the process following process qualification, first article inspection, and successful part validation via laboratory examination and testing. Once frozen, no changes to process parameters are permitted without time-consuming and costly re-validation. Validation of new manufacturing methods (or even an adaptation of an existing method) can easily exceed a timeframe of two to four years.


ACCENT will allow the European aero-engine manufacturers to improve their competitiveness by applying adaptive control techniques to the manufacture of their components. Being able to adapt the machining process to the constantly changing tool and component conditions whilst operating in a multi-dimensional 'approved process window', processes will be optimised to the prevailing conditions and no longer 'frozen'. Benefits will be seen in terms of reduced part manufacturing process time, more consistent part quality in terms of geometry, surface and sub-surface properties, tool usage optimisation, the elimination of costly part re-validation due to small process changes, and the possibility to improve component design due to optimised machined surfaces. Anticipated cost savings could be 40%.

Description of Work

The project is divided into five work packages (WP).

WP1: project management.

WP2: ensures that a standard procedure is generated to define multi-dimensional parameter windows for the machining process and material combinations. The outcome will be a specification which defines how a machining process has to be established and controlled in order to satisfy a defined surface integrity level.

WP3: is focused on developing the Standard Procedure for Adaptive Control. The work package will deliver an understanding of how to use process monitoring systems in a closed-loop adaptive control system that keeps the process within a defined process window.

WP4: will bring together those elements that have a direct effect on the component performance in terms of life and fitness for purpose. The interaction between the surface integrity generated as a result of the machining process parameters, cutting tool and machine tool condition, material characteristics, etc. will be investigated and understood.

WP5: exploitation and dissemination.

The knowledge gained here will allow the design function to understand the effect of machining processes on part quality and subsequent component service, and thus allow the component design to be optimised. With the new validation procedure, new demands will be placed on storage and retrieval of related data.

Expected Results

For the manufacture of critical aero-engine components, ACCENT will develop a standard procedure for defining process parameter windows and develop methods whereby components manufactured within these process parameter windows are validated to meet the demands of design and surface integrity requirements. It will provide a new manufacturing methodology that will allow significant reduction in recurring validation costs and develop a novel standard procedure for adaptive control based on process monitoring techniques. It will take account of factors responsible for producing variable part quality and provide aero-engine manufacturers with a methodology that can be adapted to individual company procedures, thus allowing the design and manufacture of critical components to be optimised. As the majority of Europe's aero-engine companies are project partners, increased contacts will lead to new collaboration opportunities and consolidation of the aero-engine sector in Europe. ACCENT will involve world-leading experts from both universities and companies in Europe, thus helping to increase the synergy between academia and industry, and help to secure a supply of highly skilled young aero-engine engineers in Europe.