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NOMENCLATURECER cost estimating relation DEE design and engineering engine FSW friction stir welding KBE knowledge based engineering t delay delay time before a manufacturing operation τ 0 time it takes to reach 63% of the steady state speed of a manufacturing process ν 0 steady state speed of a manufacturing process x variable on which manufacturing analysis are based, for instance length or area INTRODUCTIONTo remain competitive in a rapidly changing and customer driven industry manufacturers are implementing integrated and collaborative design methodologies and are looking for cost effective manufacturing methods. The integrated and collaborative design methodologies are generally addressed as concurrent engineering. Manufacturers are realising that knowledge is the intellectual capital of the enterprise and as such are embracing a philosophy known as knowledge based engineering (KBE) to enable and facilitate concurrent engineering. Cost effective and efficient manufacturing methods are usually methods that can be automated and which produce reliable and appropriate results. For joining different metallic parts, friction stir welding (FSW) fits these ABSTRACT Multidisciplinary design and innovative highly automated manufacturing methods are increasingly important to today's aircraft industry: multidisciplinary design because it reduces lead-time and results in a better design, and automated manufacturing methods because they are more capable and reduce manufacturing cost. In this paper a cost estimation model is presented that integrates the manufacturing cost of friction stir welded connections within a multidisciplinary design decision tool. Due to the fact that friction stir welding is a new manufacturing method, the cost estimation model is based on the actual process physics, meaning what the process looks like in terms of processing speeds and characteristics. As an integral part of a multidisciplinary design framework, the developed cost estimation model contributes to a design support tool that assesses not only manufacturing but also structural and aerodynamic issues. It is shown that the cost model developed can be integrated into this more holistic design process support architecture. The predicted costs are accurate to the historical data and allow tradeoff of manufacturing and economic considerations within the context of the multidisciplinary design tool. The tradeoff capability is highlighted through a presented case study that compares the friction stir welding process as an alternative solution to more tradition riveting. Most importantly, this results in a quantitative tradeoff between two processes that shows the manufacturing cycle time of friction stir welding to be reduced by 60% and the recurring assembly cost by 20%.

The design and production of aircraft structures is a highly cost-driven industrial activity. Advanced, more reliable cost-estimation techniques can help to improve competitiveness and reduce risk in the bidding phase. In this paper a design support framework will be presented that offers improved information and knowledge about new designs in an early stage of the development. The paper focuses on aircraft movables but similar frameworks can be built for other product families. The framework is based on the design and engineering engine architecture. The design and engineering engine formalizes the basic design cycle and comprises a multi-model generator (MMG) based on knowledge-based engineering principles that creates a smooth link between a parametric product model and different analysis tools, including a cost analysis tool. It will be shown that such an MMG can support the extraction of a cost engineering view on the product model that can be used in combination with proper cost-estimation relations to have more reliable cost information in an early stage of the design process. A cost analysis tool is presented that resembles a cost representation of a factory. The cost engineering view extracted by the MMG is fed into the cost analysis tool to give the designer an estimate of the cost consequences of his or her design choices. Emphasis is put on the influence of the choice of manufacturing concept on costs.

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