Geometrical tolerancing in process planning: a tridimensional approach

A method to perform tridimensional analysis and tridimensional synthesis of machining tolerances is presented. The model relies on the small displacem ent torsor concept and on the computer aided tolerancing approach. The link between process planning and functional tolerances with torsor chains acco rding to workpiece set-ups is exposed. An example shows how the model is us ed to determine automatically geometrical variations of the workpiece knowi ng geometrical variations of each part (part-holder, positioning devices, m achined surfaces, etc.).