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One recent evolution in commercial transport structure has been the emergence of monolithic structure applications. Monolithic structure reduces the number of parts that must be managed, eliminates sub-assembly operations and contributes strongly to determinant assembly practices. The cost of three components from the Boeing 737-200 and their counterparts on the Boeing 737-600 will be compared. The mid 1960's 737-200 components were assembled from sheet metal details. The mid 1990's 737-600 components are monolithic designs and utilize superplastic forming, casting and NC machining technologies. The built-up solutions and the monolithic solutions are compared based on cost infrastructures from the 1960's and the 1990's.

Process development work was conducted to develop a machined fuselage frame concept for a small (5 abreast) commercial airplane. To minimize detail fabrication cost and to facilitate lean manufacturing, roll forming was identified as the preferred forming process. To reduce assembly costs, long frame segments were desired to minimize the number of frame splices. Since plate stock is limited to lengths of approximately 3.66 meters (12 feet), formed aluminum extrusions were selected as the raw material form. Roll forming and stretch forming process paths were screened for both J section and rectangular bar extrusions. The post machining distortion produced in formed extrusion and plate hog-out frame segments was compared to each other and to process standards governing allowable fit-up forces. As a result of this process development activity, a producible roll forming process path was developed.