Tolerance evaluation system of manufactured parts based on soft gaging

Abstract

This report deals with soft gaging as an inspection technique for manufactured parts. First, we propose a modeling of soft gaging for inspection of tolerances on features with or without a relationship between the feature and the datum. The soft gaging model that conforms to the geometric tolerance standards is represented using ISO 10303-11 EXPRESS-G notation. We also propose mathematical definitions of soft gages for such tolerances and the procedure for the evaluation of such tolerances of machined parts based on a CMM measured point set in this paper. Second, we develop a tolerance evaluation system of machined parts based on the proposed soft gaging and a fitting procedure based on a small displacement screw method considering spatial constraints, which enables the fitting of the soft gage into a measured point set of the machined parts and thus deriving a deviation. Finally, we also show that the proposed method is very effective in its application to certain inspection examples.