Automatic dimensioning in design for manufacturing

Mwhattical 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 app=r, reseach 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. 1,0 Introduction: Why Automatic Dimensioning ? One of the main problems facing modem industry is the need to reduce the product design cycle in order to stay competitive in today’s market. The time cycle affects two important factors: cost and the ability to respond quickly to changes in the market and technology. Two major bottlenecks occur in the product design cycle as shown in Figure 1. The first bottleneck occurs at the interface between the conceptual design stage and the design analysis/refinement stage. The second occurs between the second stage and the product manufacturing stage. Most of today’s integration efforts are directed at the interfaces between Permission to copy without fee all or part of this material is grsnted provided that the copies are not made or distributed for direct comrnercist advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for Computing Machinery, To copy otherwise, or to tepublish, requires a fee and/or specific permission. @ 1991 ACM 089791427-9/91/0006/0379 $1.50