Inspection Method for Geometrical Tolerances using Coordinate Measuring Machine

Abstract

The method of inspecting geometrical tolerances is important from the economic and qualitative viewpoints in Coordinate Measuring Machine (CMM) measurement. Much work has been done on the evaluation of the geometrical deviation of form for a single feature from a measured data set. But, on the other hand, the inspection of geometrical deviation for related features has not been well developed. In this paper, we first discuss the following topics: l)Problems of CMM inspection based on ISO Geometrical Tolerance, 2)Formal representation of ISO geometrical tolerance using EXPRESS, and 3)Necessity of a virtual gauge as a criterion for deriving geometrical deviation. Secondly, we propose a virtual gauge as a criterion for deriving the geometrical deviation of the toleranced feature from a measured data set. For the mathematical representation of the virtual gauge, we introduce mathematical representations of geometrical elements and the relationship between datum and toleranced feature. We extend the small displacement screw method in order to find out the minimum geometrical deviation based on the virtual gauge. We also show that the proposed method is very effective by applying it to some examples.