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Throughout the development cycle of an assembled product, design and manufacturing engineers commonly perform ad hoc studies to determine whether their creation will meet its dimensional objectives. More simply, they answer the question, “will it go together and work right the first time?” These studies usually involve adding the maximum tolerance allowances in a single direction to find the maximum possible error. Known as a “worst case” study, this method underestimates the accuracy of an assembly because it assumes each part is always manufactured at the extremes of its specification limits. This paper proposes and describes the featurized datum flow chain as an adaptive and comprehensive alternative for calculating predicted variation in characteristics of assemblies. The paper advances prior research performed for the Lean Aircraft Initiative at the Massachusetts Institute of Technology, and it offers an example for completing an assembly study.

Two critical milestones that must be achieved during concept design are 1) definition of a product architecture that meets performance, producibility, and strategic objectives, and 2) estimation of the integration risk in each candidate concept. This paper addresses these issues by describing the role played by the producibility members of an Integrated Product Team (IPT) during concept design. Our focus is on the execution of the what we call the “chain method”, which illustrates the structure of function delivery in a concept in a simple pictorial way and helps the IPT to understand the advantages or disadvantages of using a modular or an integral product architecture. The producibility members play a central role in capturing and evaluating the chains for different candidate concepts and decompositions.