Study Of Efficient Tool Path Planning For Machining Free Form Surface Based On UG Customization

Free form surface is commonly seen in automobile, ship , die and mould industry. The efficiency and quality of manufacturing such surfaces is becoming more and more important, especially when five-axis CNC machines are widely used.Tool path generation method is one of the most important steps in free form surface machining. It is known that the length and smoothness are two important indexes in evaluating a tool path. With all other machining parameters being the same, a shorter tool path could not only improve efficiency, but also reduce tool wear and the chances of breakage. Moreover, reduced CL file size could save the memory in the CNC controller, therefore, it would be of significant importance to develop such a tool path generation method which could generate shorter tool path. In this thesis, an improved constant scallop tool path method for machining free form surface is introduced which is not only efficient but also overcomes problems associated with dramatic tool path direction changes. With the scallop height kept constant, it is shown that tool path generated by this method is shorter than that of Iso-planer method, Iso-parametric method and traditional constant scallop method, which means the proposed method is more efficient.Interference is another important concern in machining free form surface. A Tool Orientation Traversing method is introduced in this thesis. The status of interference is determined by checking the Boolean result between the tool and workpiece. Then a serie of interference free tool orientation is identified along the tool path, we can select the optimal tool orientation under the requiremnet of minimal tool swinging angle. This method not only avoids interference, but also produces smooth tool orientation series in the machining process, thus the impact on tool and workpiece caused by abrupt change of tool orientation is eliminated.The proposed methods are integrated with the commercial CAD/CAM/CAE system Unigraphics NX. A user friendly software module is developed so that programming time of five-axis machining is significantly reduced. A mathematic model of Mikron UCP 800 Duro is also built in Vericut to validate the proposed methods and software modules. At last a cutting experiment is performed on an integrated impeller to validate the proposed methods.