Research On The Normal Vector And Curvature Estimation Algorithm For Triangular Mesh Surface In CNC Machining

CNC machining technology is widely used in the field of aerospace, automobile,shipping, machine tool and die-mold industries because of its flexibility, highprecision and efficiency. In CNC machining of triangular mesh surfaces, theestimation accuracy of normal vector and curvature on triangular mesh surface arecritical to tool path planning and quality of machining.This paper is focused on how to improve the estimation accuracy of normalvector and curvature on triangular mesh surface and aims to improve the calculationaccuracy of cutting location points and machining precision of triangular mesh surface.Some details investigated in this paper are stated as follows.Firstly, a triangular shape factor is introduced and an accurate algorithm isproposed for evaluating the nodal curvature for triangular mesh. The case study anderror comparison demonstrate that the algorithm can effectively improve the accuracyand stability of nodal normal vector estimation for triangular mesh. The accuratenormal vector of the points on the triangular mesh can be computed by nonlinearlyinterpolating the adjacent normal vectors. The influence of accuracy and stability ofnormal vectors upon smoothness of tool path, stationary of CNC machining andmachining precision of the triangular mesh are discussed in details.Secondly, Taubin’s method for curvature estimation is optimized. Theinterpolation calculation is simplified to estimate curvatures of points inside thetriangles. Then, the effect of accuracy and stability of curvature estimation on chorddeviation, scallop height, path interval and step length are researched. the case studyand error comparison demonstrate that the optimized algorithm can effectivelyimprove the accuracy and stability of curvature estimation for triangular mesh.Finally, tool path of triangular mesh surfaces is planned by iso-scallop method.Results of The machining process simulation show that normal vector and curvatureestimating algorithm in this paper can effectively improve the calculation accuracy ofcutting location points and machining precision of triangular mesh surface, which issignificant to CAE/CAM integration.