Complex shaped panels used in the aeronautical and space industries are made by chemical milling. This process is frequently used on double-curvature parts requiring weight reduction or in parts made from alloys of titanium, tin, nickel, cobalt and magnesium. Main environmental problem associated with the process is the production of a large amount of slurry that are currently disposed of by burning in cement kilns. The process also uses large amounts of water and solvents. Mechanical milling represents a better environmental alternative to the process.
The beneficiary, DUFIEUX Industrie, has made a technological leap in machine tool design that enables complex shaped panels to be mechanically manufactured with at least the same level of efficiency as chemical milling. In this eco-friendly process, the only by-products are aluminium chips that are recycled as secondary raw material. The project aims to demonstrate the performance of the mechanical milling with the partnership of Airbus. Milled panels are important for the plane industry needs because they allow aircrafts to carry greater weight. As a result, the panels significantly reduce oil consumption without impairing the rigidity of the plane.
The project demonstrated the technical capacity of mechanical milling of double curvature panels. It designed a model F5X1 demonstrator that could rapidly replace the chemical milled panels with the new mechanical ones. The model can process panels of 6.5 m long and 2.5 m wide. It is believed that it can be developed to process panels of 10 m long and 4 m wide.
The project had to overcome existing technical problems associated with mechanical milling. It was difficult to achieve accurate machining, sufficiently good dynamic performance of the machine and quality of the controls and spindles. The project overcame these difficulties by incorporating several technical innovations in the F5X1 demonstrator including:
- High-speed, high-performance electric spindles.
- Expertly designed “mecatronic” systems and optimised machine design.
- Digital closed-loop control management and introduction of induction motors.
- Digital machine control.
The beneficiary added two major innovations to these technologies:
- 100C milling head allowing an optimised tool path with limited amplitude during the machining process.
- The mecatronic support: an intelligent support mounted on a 6 axis module facing the tool and perfectly synchronized with the 6 axis milling head.
Patents have been registered for both these technological innovations. As a result of such technological innovations, the clean technology implemented in the GAP project pilot demonstration unit is a world first and a major technological step for the aeronautical and space industry.
Airbus is already building a plant that would produce different size units according to the panels needed. Mechanical milling will replace the chemical milling for all panels produced by Airbus. The beneficiary is in contact with the IPPC bureau in Spain for the technology used in the project to become a Best Available Technology. Potential clients are interested in using the process for other materials such as titanium or carbon fibre.
The economic and environmental benefits of replacing chemical milling with mechanical milling at Airbus’s European sites are estimated by the beneficiary as follows:
- a reduction in the required quantity of rinsing water by 225 000 m3 per year,
- a reduction in the quantity of waste produced by more than 16 000 tons,
- total elimination of sludge processing and associated risks from hydrogen emission,
- a 50 % reduction in operating costs,
- a 20 % reduction in the cost per machined part,
- a 50 % reduction in the production cycle time,
- a 57 % reduction in electricity consumption.
This project has been selected as one of the 21 Best LIFE Environment projects in 2007-2008