More and more customers (and frequently relatively major customers) are no longer demanding product drawings or 2D CAD files from their suppliers but rather 3D product models which they can then work on further in their own (3D) systems. In such cases the use of a 3D CAD system can be essential if competitiveness is to be retained. The most important advantages a 3D CAD system can offer over a 2D system are: more complete product models, fewer documents which need to be created and managed individually, because a large number of documents can be generated (semi-)automatically from the 3D product models (such as drawings, bills of material, operation sheets, assembly and operating instructions, spare parts catalogues), early detection and prevention of functional, manufacturing and other problems, resulting in fewer op