Research On Five-axis CNC Interpolation Technology Based On NURBS Surface Geometric Parameters

Five-axis CNC machining is gradually replacing traditional three-axis machining in the manufacture of complex free-form parts due to its better surface finish quality and higher machining efficiency.However,due to the high complexity and difficulty of five-axis NC machining,there are still some problems to be solved in the five-axis machining direct interpolation technology and the complete description of the surface geometry information.For this reason,the research on five-axis CNC interpolation technology of NURBS surface has been carried out in this paper.The mathematical description of the NURBS curve and surface is studied.The homogeneous coordinate method is used to simplify the calculation of the point on the NURBS curve surface and the calculation of the partial derivative.The storage method of NURBS surface entity in IGES and STEP data exchange files is analyzed.Based on this,Visual C++is used to extract the base function power and node vector describing NURBS surface from the above two data exchange files.Software for geometric parameters such as weight factors and control point coordinates.The extracted parameter data provides a source of data for subsequent imputation calculations.A mathematical model of five-axis NC direct interpolation of NURBS surface is established and its algorithm implementation is given.Using the isoparametric line method to plan the tool path,then a simplified algorithm is proposed to calculate the tool contact coordinates,which ensures the real-time interpolation.Finally,the inverse kinematics transformation is completed in combination with the specific machine structure to generate the command value to control the machine tool.Based on the above interpolation mechanism,the interpolation algorithm is implemented by Visual C++software programming,which can complete the input of NURBS surface parameters,tool path planning,tool contact and tool offset calculation,machine inverse kinematics transformation,the command value of the machine tool movement and other work.Finally,the NURBS surface five-axis interpolation algorithm proposed in this paper is simulated and verified by the example application simulation and verification.The simulation results verify the correctness and feasibility of the proposed interpolation method.