Toward a Theory for Design of Kinematically Constrained Mechanical Assemblies

This paper summarizes a theory to support the design of assemblies. It describes a top-down process for designing kinematically constrained assemblies that deliver geometric key characteristics (KCs) that achieve top-level customer requirements. The theory applies to assemblies that take the form of mechanisms (e.g., engines) or structures (e.g., aircraft fuselages). The process begins by creating a kinematic constraint structure and a systematic scheme by which parts are located in space relative to each other, followed by declaration of assembly features that join parts in such a way as to create the desired constraint relationships. This process creates a connective data model containing information to support relevant analyses such as variation buildup, constraint analysis, and establishment of constraint-consistent assembly sequences. Adjustable assemblies, assemblies built using fixtures, and selective assemblies can also be described by this theory. KEY WORDS—assembly, kinematic constraint, determinate assembly, screw theory, tolerance analysis of assemblies, feature-based design of assemblies, assembly-sequence analysis