A unified approach for computer-aided precision machining of parts having sculptured surfaces.

摘要

The main objective of this research is to advance the state of the art in CAD/CAM-based manufacturing of parts having sculptured surfaces in the areas of part surface modeling, tool path generation as well as cutting force modeling.;In surface modeling area, an effective computer aided sculptured surface design technique is proposed. The technique models part's sculptured surfaces in such a way that it warrants a smooth "jerk" transition at the common boundaries of the surface patches of the part. Three theorems concerning the necessary jerk continuity conditions for surface-patch connections are derived and their proofs are presented.;In tool path generation area, an adaptive CNC tool path generation algorithm for precision machining of parts with free-form surfaces is proposed. Because of its adaptive error correction mechanism, the algorithm is robust and is able not only to replicate the contour of the desired curve/surface but also to guarantee that the path generated meets a specified tolerance.;In cutting force modeling area, a new three-dimensional cutting force model in end milling for sculptured surface machining is developed. The model includes a comprehensive set of realistic and significant cutting parameters such as normal rake angle which has a marked effect on the cutting force calculation. By representing the rake surface of a flute by an osculating plane, the proposed model yields three-dimensional cutting force expressions in two steps, that is, (1) determine the magnitude of the resultant cutting force acting on the flute, and (2) find the location of the line of action of the resultant force by using the method of principle of moments. Additionally, since the axial depth of cut must be known for machining a sculptured surface, an innovative axial depth of cut estimation method has been proposed within the proposed model. Computer simulations of the cutting force model have been performed in terms of mechanic response of cutting. The results have been encouraging. Furthermore, the proposed model has also been used to design an optimal cutting tool.