Tolerance specification and comparative analysis for computer-integrated dimensional inspection

Abstract

Two important issues in the development of a computer-integrated dimensional inspection environment for manufactured parts are described, namely tolerance specification and comparative analysis. These two issues are related directly and therefore, should be addressed together. For supporting the computer-integrated dimensional inspection, a geometric dimensioning and tolerancing (GD&T) specification module and a comparative analysis module are developed and integrated with CATTA of the IBM CAD/CAM system. The proposed specification module supports ISO and ANSI geometric tolerances and allows multiple tolerance assignments on each single feature as well as on a group of same pattern features. Using this specification module, various tolerance information can be directly specified to the 3D CAD model of a part and can be used to support the subsequent planning and operation for manfacturing and inspection. The comparative analysis module is created to work with the GD&T module for constructing datum reference frames and comparing the actual measurement data with nominal design. After specifying all necessary tolerance information, using discrete measurement data from coordinate measuring machines (CMM), one can evaluate the dimensional quality of an actual feature through the comparative analysis module.