CFRP How CFRP drastically reduces the production times of aircraft doors

The manufacture of doors for passenger aircraft is predominantly manual work. The assembly of the door structures with their bolted and riveted joints is particularly time-consuming. In a research project by Fraunhofer IWU, Fraunhofer LBF, Trelleborg and Airbus Helicopters, the production time for the door structure has been reduced from 110 to just 4 hours.

When manufacturing doors for passenger aircraft, many intermediate steps are required to avoid direct contact between different materials, which leads to corrosion. If thermoplastic carbon fiber composite materials (CFRP), which can be automatically welded together without separating layers, are used instead of aluminum, titanium and thermosets, the production time for the door structure is reduced from 110 to just 4 hours. This is the result of a research project by Fraunhofer IWU, Fraunhofer LBF, Trelleborg and Airbus Helicopters.

Together with our colleagues from Airbus, we took a close look at all the door structures in order to adapt the geometries for automatic clamping and joining.

Dr. Rayk Fritzsche

Another key to shorter assembly times lies in the modular design for different aircraft door variants. To this end, the project team went on a targeted search for components in different door models that could be standardized. They found what they were looking for in the cross member, for example. The researchers designed a fully automated assembly line for the most common models and developed fixtures and clamping elements that are suitable for resistance welding and ultrasonic welding joining technologies.

From the manufactory to the tightly synchronized industrial production process

Dr. Rayk Fritzsche, project manager at Fraunhofer IWU: "Together with our colleagues from Airbus, we took a close look at all the door structures in order to adapt the geometries for automatic clamping and joining. As a result, we were able to reorganize the individual assembly steps and automate them throughout. This means that only a fraction of the previous throughput time is required." Only the installation of the locking mechanism still requires manual work.

Two largely identical assembly and joining lines are now planned so that replacement capacity is available if one line fails (redundancy). As a result of various standardization measures, 10 doors each can be combined into one batch before the line is fully automatically converted for the next model series at the end of the shift. In relation to the capacity of 4,000 doors per year, the new material and production concept results in a considerable economy of scale.

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Is it worth investing in new production facilities?

Maxi Grobis from the IWU Factory Planning, Simulation and Evaluation team simulated all technical and economic aspects of the new assembly line - which are usually mutually dependent. The most important technical evaluation criteria include the complexity of the product and production process, automation opportunities and risks, also from the perspective of flexibility and adaptability or the overall system availability in a chain of different individual automations.

In order to come up with a solution from a single source, we looked at the entire production and assembly process for the door and transferred it into a dynamic cost calculation.

Maxi Grobis

Automation for automation's sake was not an option. Grobis emphasizes: "In order to come up with a solution from a single source, we looked at the overall process of production and assembly of the door and transferred it to a dynamic cost calculation. After all, what works technically should also be coherent in terms of acquisition costs, machine hour rates, maintenance costs, energy costs, capital commitment and depreciation. Simply pointing out the potential savings in labor costs or through shorter throughput times would not be enough."

The newly developed automation solution was to be implemented taking into account all technical, logistical and economic criteria. Grobis is particularly proud of the fact that it was also able to reduce planning times by around a quarter with its integrated simulation approach: If you think about business management from the outset, you save yourself unnecessary change loops right from the planning stage.