A DIMENSIONING AND TOLERANCING ASSISTANCE MODEL FOR CAD-CAM SYSTEMS

A model called TTRS for technologically and topologically related surfaces, has been developed and its application to dimensioning and tolerancing is presented here. According to this model, any part can be represented as a succession of binary surfaces associations forming a tree. Additionally, each surfaces association, termed as a TTRS object, is represented by a set of minimum geometric datum elements (MGDE). Once established, each TTRS can be given appropriate geometric dimensioning and tolerancing (GD & T) symbols through a general procedure making use of GD & T tables and combination rules. Application examples are also presented.