CAD-directed programming of a vision-based inspection system

A major difficulty in developing the link from computer aided design (CAD) to automatic part inspection involves extracting the dimensioning and tolerancing information from a part drawing. This design information must be associated with the corresponding geometric features when controlling an inspection machine. In this paper, a methodology is developed for extracting the necessary design information from a CAD system to control a two-dimensional video inspection system. Information regarding part geometry, datums, and geometric tolerances and dimensions is generated during the design process and written to machine-independent data files. This information is then post-processed to automatically generate inspection programs for a specific inspection machine. This computer aided inspection system provides a foundation for research in the area of CAD-directed inspection. Because the system is modular, additional capabilities may be added to increase the efficiency of the process or to support other inspection devices. The computer aided inspection system demonstrates the concept of automatically controlling a measurement machine using CAD design data.