Reverse engineering of free-form surfaces

Abstract Reverse engineering is used in different areas of design and manufacturing. In the automotive industry it is often necessary to change the shape of the prototype during the manufacturing process. The changes have to be then considered in the drawing and in the geometric model of some parts in CAD system. It is associated with the measurements of the part surface and its approximation. The authors of this paper have concentrated on presenting methods of measurement and of the geometric modelling of free-form surfaces. An integrated solution of these tasks will be proposed. The identification of the object with coordinate measurements is discussed. Measurement results are written in the format ready for use by the program of the surface approximation. This program was created by the authors of the paper. The NURBS method is used for surface description and the problem is solved by the least squares method. The results of calculations are written in the macrostatement format (for the definite CAD system) or in a way using the more universal IGES standard. Two integrated CAD/CAM systems are used in the research (Personal Machinist and Mastercam). In the CAD module, visualisation of the geometrical model is effected. The CAM module is used for generating the cutter path for CNC milling machines. The machined parts are measured for the purpose of determining of the manufacturing accuracy. This is carried out on the CNC milling machine with a special probe.