Designing assemblies

This paper presents a theory to support the design of assemblies. It brings together prior work in a new synthesis, resulting in a top-down process fo r designing assemblies so that they deliver geometric Key Characteristics ( KCs) that achieve top level customer requirements. The theory applies to as semblies that take the form of mechanisms (e.g. engines) or structures (e.g . aircraft fuselages), but has less relevance to assemblies that take the f orm of connective or distributive systems (e.g. hydraulic piping). The theo ry shows how kinematically constrained (statically determinate) assemblies can be unambiguously designed to satisfy geometrically-defined customer req uirements. The top-down process presented here begins by creating a kinemat ic constraint structure and a systematic scheme by which parts are located in space relative to each other, followed by declaration of assembly featur es that join parts in such a way as to create the desired constraint relati onships. This process captures design intent by creating a connective data model that contains information to support relevant analyses such as variat ion build-up, constraint analysis, and establishment of constraint-consiste nt assembly sequences. Adjustable assemblies, assemblies built using fixtur es, and selective assemblies can also be described by this theory. Problems arising from multiple KCs and KC conflict can be identified. Issues unreso lved by the theory are also noted.