On the Role of Geometry in Mechanical Design

Introduction A complete design usually specifies a mechanical system in terms of component parts and assembly relationships. Each part has a fully defined nominal or ideal form and well defined material properties. Tolerances are used to permit variations in the form and properties of the components, and are used also to permit variations in the assembly relationships. Thus the geometry and material properties of the system and all of its pieces are fully defined (at least in principle). Henceforth we shall focus on geometry and, for reasons that will become evident, will not deal with materials despite their obvious importance. Mechanical systems specified in the manner just described meet functional specifications that appeared initially as design goals. The process of design can be thought of as 'generating the geometry' ... the breakdown into components with coarsely specified geometry, and then the detailed specification of the component forms and fitting relationships. Design