Evaluation of 3-D feature relating positional error

Position tolerance is a three dimensional geometric specification used to c ontrol the location of features of size with respect to a set of datum feat ures or with respect to each other. Among features of size, hole is perhaps most frequently encountered in the production of industrial parts. To cont rol the relationship between a set of holes, feature relating position tole rance (referred to as FRTZ) is used. FRTZ is applied to ensure proper assem bly between mating parts. Assessment of feature relating positional error i s a difficult task due to the absence of a datum reference frame whose func tion is to impose translational and rotational constraints on the part. Exi sting techniques for the assessment of FRTZ are either too expensive, or ti me consuming and inaccurate. This paper presents a mathematical model of th ree-dimensional feature-relating positional error and proposes a sound meth odology for its evaluation. The results of performance analysis indicate th at the proposed methodology is robust, accurate and efficient. The procedur e has been implemented in a computer-aided inspection system. (C) 2001 Else vier Science Inc. All rights reserved.