The maintenance, repair and overhaul (MRO) of aero engine components consists of a chain of different processes, e.g. inspection, de-coating/coating, welding, milling and polishing. Currently most of these processes are carried out manually. At present the supply industry is developing improved machining equipment to automate the individual process steps.
Nevertheless, the single repair processes remain separate and unconnected. For example, data acquired during the incoming inspection are put down on paper and are not available in electronic form for subsequent repair operations. Therefore, even though the single repair operations may be automated, it is also beneficial to improve the overall process by extending data flow and factory automation throughout the entire MRO chain.
AROSATEC was proposed in the 1st call of the 6th EC framework programme and addresses these issues.
The objectives of the project were:
- To improve existing repair methods by employing adaptive machining technology. The adaptive CNC technologies make use of the information provided by the data management system and compensate for the part-to-part variation of the complex components to be overhauled. The data flow between the adaptive repair steps optimises the single repair technologies as well as the efficiency and the flexibility of the entire chain of repair processes for aeroengine components.
- To develop a data management system which constituted the core of automated overhaul systems for aeroengine components. As part of this innovative data management solution, the single repair process modules are integrated to build an automated repair cell for aero engine components. Furthermore, it is possible to establish 'virtual' MRO workshops. The data management system generates a data set for each individual component and handles the logistics of the components and the accompanying data sets.
As a result, different MRO processes can be carried out at different facilities without loss of information, efficiency or quality. In addition, the approach described supports efficient life cycle monitoring.
The project activities have been grouped into six workpackages:
- Management (WP1), which carried out the general and administrative management of the activities, as well as those concerning the dissemination and exploitation;
- Specification (WP2), which analysed present and future requirements of the system, defined the standardisation of data structure, and tested the compatibility with end user systems;
- Process R&D (WP3), which optimised the necessary technologies (scanning, laser welding, milling, and adding adaptive machining technologies to laser welding and milling);
- Software R&D (WP4), which developed the structure of database, data flow, data distribution, process interfaces and management;
- Integration (WP5), which studied the technology and data integration;
- Testing & Demonstration (WP6), which tested and demonstrated the entire system.
In the first period, the project investigated the end user requirements. The repair processes to be incorporated in AROSATEC was defined, resulting in the detailed requirement specifications. These were analysed by the partners and compared to technologies already available. The gap between contemporary technology and requirements was defined for the development needs and goals for AROSATEC.
While setting up the detailed requirement specification, the improvement of the scanning process and the definition of the data-treatment optimisation was started. In the course of AROSATEC new scanners were tested and optimised, software interfaces were optimised and adapted to each process of the process chain. Additionally, the general layout of the data backbone was set up and the concept tested and verified.
The efforts was then dedicated to optimise the different repair steps, from scanning to laser welding and to adaptive machining. While scanning improvements can be made with the use of new, high accuracy scanners, welding demands sophisticated tooling, especially for complex geometries like on nozzle guide vanes, and intelligent welding strategies. This goal can be reached by adding adaptive technologies to the welding process.
A major problem for the adaptive machining was to fulfil the requirements of the MROs. All parts have to be processed in the given tolerance range although the geometry of each repair part is unique and not equal to the new part description. Additionally, the data backbone was developed and improved and all process steps were equip
Key results achieved during the project work are:
- improvement of the optical scanning system;
- automation of the scanning process using macro functionality;
- implementation of adaptive technologies into the laser welding process;
- improvement of the milling process by adding adaptive technologies;
- set up of data management system able to store all relevant data and providing the data backbone for the connection of all process steps.
Scanning small filigree parts with shiny surfaces is a problem for optical scanning systems. In case of aero engine parts it is often not allowed to spray the parts to get a matted surface. In AROSATEC the scanning methods could be improved so that the laser power can now be adjusted to the surface properties, automatically. With this good scanning results could be achieved even under difficult conditions.
In case of the repair of aero engine parts a complete series of parts has to be processed. To automate the scanning process macro functionalities have been integrated into the scanning system. So the set up procedure is required only once for a series of parts. After the set up the system is able to run in an automatic mode. Here not only the scanning is realised furthermore the necessary calculation of the specific dimensions etc. are carried out.
One requirement for the laser cladding application is to generate the geometry of the part 'near net shape'. This means that the MRO is expecting a very precise shape of the cladded part. There are two reasons for this. First the powder is extremely expensive, so that it is economic to uses as less as possible. The second reason is, that material which had been added has to be removed down to the parent geometry. So a huge amount of weld implies a long and expensive milling process. All these requirements could be met by adding adaptive technologies to the welding process. So the cladding can now be adjusted to the individual shape and the process itself can be influenced by various parameter.
The adaptive technologies have also been integrated into the milling process. Here the requirements concerning the exactness of the milled shape are challenging. So, its is not possible to use one standard NC programme for the repair of a series of run engine parts. Each part has to be measured first, so that the NC programmes used for tip or edge repair can be adjusted to each individual repair part. With this approach the requirements of the industr
T1: For meeting the requirements concerning the process automation and the accuracy of the repaired geometry it is necessary to integrate 'adaptive technologies' to the commonly used process technologies. Only using 'adaptive technologies' allows geometrical adjustment of the numerically controlled processes, so that each individual repair part can be treated individually.
T2: Setting up a data management system used as a backbone for connecting the several automated process steps is the basis for integrated repair or manufacturing systems. Therefore, each process step has to be equipped with the corresponding interfaces. Here XML is suitable to transfer and store different types of data in a common way.
T3: Only if a data management system in combination with linked processes is used, it is possible to monitor the repair of aero engine parts on part level instead of job level. This will become an important detail in the upcoming developments in MRO industry.