Advanced Characterization of Free-form Surfaces in High Precision Machining

Precision free-form components are functionally complex objects with very accurate surfaces. In the manufacturing of these parts the complete and correct characterization of geometrical errors is an important aspect since it allows the adoption of preventive actions to control errors causes such as the thermo-mechanic behaviour of the machine tool, the removal mechanism of the cutting operation, the wear of the tool, the lubricant action, etc. In this work an advanced method of geometry characterization has been adopted to investigate the various contributions of the geometric error, resulting from the machining of any free-form geometry. The method allows the effective estimation of the size contribution error as well as form, orientation and position deviation. The method consists in an iterative process that minimize the distance of the cloud of points measured to an optimized offset of the nominal model of the component. At the end of minimization process, optimal parameters are used for the complete shape characterization of the part.