Automatic dimensioning in design for manufacturing

Abstract

Mechanical design concepts evolve from rough sketches at the preliminary design stages to full working drawings at the detail design stage. Although commercial computer based tools for the conceptual design stage have just recently begun to appear, research in this area has existed for some years now. Existing preliminary design tools allow the designer to generate the shape (topology) of a component without defining the dimensions. In order to perform any modifications to the geometry the geometric entities (points, lines, etc.) must be constrained via dimensions. Parametric Modelers and Variational Geometry Systems, are examples of such technology, which are becoming popular design tools. In these systems the components must be correctly dimensioned by the designer before the geometry can be manipulated. There is no unique dimensioning scheme and selecting a consistent dimensioning scheme is a non-trivial, error prone task for any geometric component of reasonable complexity. Computational tools at this stage will be extremely valuable to the designer, not only as a means to completely dimension an undimensioned component but to complete a partially dimensioned design conserving the designers intent. The paper describes a graph theoretical approach to the automatic generation of geometrical constraints as part of an automatic dimensioning preprocessor for Variational and Parametric Systems.