Representation of feature relationship tolerances in solid models

The need for representing tolerance information in solid modelling has spawned significant research activities leading to tolerance theories and frameworks. However, the problem of ensuring validity of tolerances specified on feature/entity relationships such as distance, relative location, orientation and runout has not been adequately dealt with in these theories and frameworks. The system reported in this paper uses concepts of generated dimensions, direction vectors and dimension trees to facilitate valid representation of such tolerances in component solid models. Application of the proposed concepts to various types of multiple-entity tolerances has been illustrated. The paper also identifies some tasks of the product cycle where the proposed concepts can be utilized.