Research On The Generation Method Of Wide-pitch Toolpaths For Free-form Surface Five-axis End Milling

The rapid development of science and technology has made the geometric models of parts in the fields of medical equipment,aerospace,and optical equipment more complicated.In recent years,with the development of precision measuring instruments and graphics processor technology(GPU),triangular meshes have been increasingly used in the CAD/CAM field due to their fast,flexible and adaptable characteristics.Since the triangular mesh model can only output a small amount of geometric information of the solid model and the data is irregularly distributed,it is not possible to adjust the tool posture well during processing.Therefore,the current research on Five-axis CNC machining of surface mesh model is insufficient,so the research on mostly limited to Three-axis machining,which results in low machining efficiency.This paper analyzes the data of triangular mesh model,precisely controls the tool posture at each tool contact,achieves maximum effective cutting radius while performing interference processing to realize the tool path generation of the complex curved surface triangular mesh model.And aiming at the non-smooth characteristic of the tool path directly generated from the triangular mesh surface model,the interpolation algorithm of the tool path is studied,which alleviates the surface quality problem of the triangular mesh CNC machining to a certain extent.(1)Aiming at the problem of disorderly and random arrangement of the information stored in the triangular grid files,the topological relationship of the triangular grid information is re-established.On this basis,a new triangular grid intersection algorithm based on Kd-Tree is proposed,which can lock the specific index position of triangle patch corresponding to each tool contact on a trajectory line.At the method of calculating the vector curvature and the corresponding direction of the contact is given.(2)With analyzing the geometric characteristics of the toroidal cutter and the triangular mesh surface,a method is proposed to maximize the effective cutting radius by changing the tilt angle and optimizing the inclination angle under the condition of no curvature interference.Finally,a new discrete model of toroidal cutter is established based on the characteristics of triangular mesh surface,and the corresponding interference detection and correction method is also put forward.(3)Studying the chord height error of mesh surface due to its own characteristics.Compared with parametric surface,if the tool location is directly used as the tool path coordinate of NC code,it will be difficult to control the tool path step length of machine tool,and there are also nonlinear errors due to tool swing,which will directly affect the machining quality of the workpiece surface.Firstly,the mathematical model of chord height error and nonlinear error is established in this paper.Then,taking the composite total error as the design tolerance,the interpolation method between adjacent tool points under the given precision condition is used to optimize the machining path.