A unified functional tolerancing approach for integrated design, manufacturing, and inspection

This dissertation research develops a systematic and scientific methodology for functional tolerancing. The methodology is hoped to provide a theoretical foundation and guidelines for tolerance design in precision manufacturing within a concurrent engineering environment.; In this research, a unified functional tolerancing methodology is developed based on concurrent engineering principles. This methodology is further tested with shop floor production data. The focal point of this methodology is that the determination of dimensions and tolerances is simultaneously integrated with product functional requirements, manufacturing constraints and metrology conditions. To implement the proposed approach, Legendre-Fourier polynomials-based tolerance parameters are introduced as a means to characterize geometry of manufactured parts. Feasibility of the proposed approach is examined in the diverse applications of design, manufacturing, and metrology. A series of studies has been accomplished with the following highlights: (1) A unified functional tolerancing approach has been developed and tested. This unified tolerancing approach will bring about substantial benefits to product quality and cost savings, particularly for precision manufacturing industry . (2) A set of novel geometric tolerance parameters has been devised. These parameters provide a means for realizing the above unified tolerancing approach. (3) The use of the proposed tolerance parameters in functional tolerancing has been demonstrated using fuel injector manufacturing data.; Another important aspect of this research is the implementation of the proposed tolerancing approach in tolerancing cylindrical parts for manufacturing process control and fuel injector parts for leakage variation control. In manufacturing process control, the proposed tolerance parameters show a strong and direct connection to machining error sources. In leakage variation control, the proposed tolerance parameters have been employed to describe the manufactured part geometry. The relationship between manufactured geometry and leakage has been quantitatively described through computational fluid dynamics (CFD) simulations. This research has demonstrated that the proposed tolerancing approach provides an effective tool for leakage variation control.; Immediate future work of this research should focus on broadening the geometric coverage to include other high payoff features such as planar features and conical features. Related mathematical characterization models for those additional features should be developed and fully explored. The ultimate goal is to develop a concurrent engineering environment within which an IPPD team may optimize product functionality, process controllability, and system measurability.