A genera/ scheme for automatic dimensioning of objects defined by solid modelling techniques is presented. The first part of the paper describes a theory that relates the geometrical definition of a solid and the dimensions that appeared on the engineering drawings. The second part demonstrates a method that automatically generates adequate dimensions from boundary representations of the solid models. Implementation of the scheme on a constructive solid geometry modeller, PADL2 of the University of Rochester, is also described.
solid modelling, dimensions, boundary representations, entities
In the manufacture of mechanical parts, dimension and tolerance information are two fundamental attributes used to describe the geometrical and functional suitability of the parts.
Current solid modelling systems require that dimensions on an engineering drawing be entered interactively or semi-automatically. In theory this requirement should be redundant as a complete geometrical definition has already been supplied in the creation of the solid model. The geometrical data should be processed automatically to generate dimensions on the engineering drawings. Provided that the solid model is a correct description of the part, the dimensions generated should be error-free and just sufficient for the definition of the part.
In this paper, the semantics of dimension are first viewed in terms of metrical geometry, and then simple algorithms for automatic dimensioning of solid-modelled objects are described for implementation in accordance with the British Standard BS 3081'2.