Investigation of micro geometry flaws in design data exchange

Geometry flaws often occur in the exchange of design data between dissimilar CAD/CAM/CAE systems, and have multiplied with the ever-increasing complexity in product geometry and the rapid growth in the number of available CAE systems (26). In recent years the international standard ISO 10303, STEP (STandard for the Exchange of Product model data), has achieved a success rate of 95-98% (24) in the exchange of design data. This project addresses not just the remaining 2-5% errors, but the exchange issue as a whole. The findings of this research help to conclude that most exchange problems are a result of incompatibility in the degrees of precision among commercially available CAD systems. The approach followed in this research involves the creation of a surface model from the information provided in the exchange (STEP) file. The surface model is then used to study the relationship between basic individual design elements such as vertices, curves and faces. This model is created in the receiver's system and all the analysis is carried out within this system to find out what is acceptable or not acceptable to the receiver's environment. The problem areas are modified to suit the requirements of the receiver's CAD environment and this new information is incorporated into the original STEP exchange file of the design model. The modified STEP file is then read into the receiver's system to get the complete manifold solid. Thus the surface model is used as a base for the entire analysis process. This approach highlights the common techniques that were repeatedly being used to solve the errors and thus define the different types of exchange errors. These errors are apparent as minute gaps ranging from 0.00001 mm-0.1 mm and can be directly linked to the precision used to associate vertices and curves with related faces.