Manufacturing and Design for Six Sigma (X-FSS)

Manufacturing and Design For Six Sigma (X-FSS) is an effective process pieced from conceptual design methodologies, axiomatic design in particular, Taguchi's off line quality methods and Six Sigma philosophy. The objective is to improve design quality in the up-front phases of the development cycle by releasing weakness-free systems at both conceptual and operational levels. Although researchers and practitioners have proposed a multitude of design methodologies pertinent to design context, such as system design, parameter and tolerance design, there is still much room for improvement. Taking a closer look at these methodologies, this research proposes a design for six-sigma process over two phases: The Conceptual Design For Capability (CDFC) phase and the Tolerance Optimization (TO) phase. The objective of the CDFC phase is to eliminate or reduce the conceptual weaknesses created in the design entity due to design axioms violation. The purpose of the TO phase is to limit coupling, a conceptual weakness, when not resolved in the CDFC phase and release the system at six-sigma quality level in all of its functional requirements. The TO features a nonlinear optimization program based on a variety of economic considerations by utilizing quality loss function (incurred by the customer) and the precision control cost (incurred by the producer). Determination of design parameters and process variables, such as mean and variance, is scrutinized for constraining conceptual weaknesses and economic design consideration. Moreover, the reasoning behind the tolerance optimization is extended to the case of multiple functional requirements within the TO systematic approach and a solution is derived to further extend its application to all levels of design mappings. A defining aspect of this research is an extensive derivation of various statistical quantities of individual design requirements by establishing several links central to Six-Sigma and robustness measures. An illustrative example is presented to demonstrate the applicability of the X-FSS process and its benefit in terms of the magnitude of design weaknesses improvement. The significance of this research is to provide an applicable process as an alternative to traditional design methodologies so that engineers will benefit from it as they embark on new design assignments.