Investigation of Feature-Based Shape Modelling for Mechanical Parts with Free Form Surfaces

This work puts forward concepts that enable the feature-based design of parts with free from surfaces in an analogous mode to those of established systems for classic regular surfaces, i.e. prismatic and conic geometry. A Bezier representation is used where features consist of surface patches. Feature para-meters are derived by referring to control points of the respective control polyhedra. Features are divided into touching, non-touching and blending. Features are under positional and/or slope continuity constraints. Constraints are checked for vadidity and warning messages are given appropriately. A case study is presented where a telephone handset is designed on a prototype system which was developed on the basis of a commerically available surface modeller. This serves to high-light the issues of feature definition possibilities, number of patches, continuity, constraints and geometry engine. A number of alternatives to the basic handset design are presented fo r illustration of the points made as well as its NC machining.