3D annotation and product data management

Abstract This chapter identifies the differences between the application of dimensions and tolerances on 2D drawings and 3D models. Based on two international standards ASME Y14.41 and ISO 16792 (which is closely aligned to ASME 14-41 but adapted to suit the ISO system). These Standards have been introduced to standardize 3D annotation because CAD systems differ slightly in the way of constructing models, assigning attributes, determining associativity and specifying tolerances. Additionally, 2D drawings can contain tolerances that are view or direction-dependent, e.g. straightness, and 3D models are not confined to orthographic views, so the positioning of tolerance indicators often requires controlling. Specifically, the indication of an Axis or Median Feature, a Projected Tolerance Zone, a tolerance zone between two points and Unilateral and Unequal Profile Tolerances are illustrated giving examples of indicating the direction of tolerance zones in 3D. An example of a part dimensioned in 2D and 3D is included to illustrate the differences. Finally, Data Management as detailed in ISO1142 is also covered, illustrating typical constituents of a data set and a 3D model.