On-machine Measurement Method Of Milling Machining Error Based On Surface Reconstruction Of T-spline Control Points Method

With the continuous improvement of mold processing accuracy requirements,it is necessary to perform error measurement analysis on the processed mold.At present,in terms of error measurement of hardened steel molds,most of them collect point cloud data on the surface of the mold through a coordinate measuring machine or a blue digital raster three-dimensional scanner.This kind of measurement method needs to move the processed mold from the processing machine to the measurement equipment.During this period,errors will inevitably occur due to clamping,which will affect the measurement results.After the mold processing is completed,the on-machine measurement system directly measures the mold on the machine tool,which saves time and improves the measurement accuracy.It shows great advantages in intelligent processing.First,the self-adaptive triangular mesh sampling point planning is carried out on the convex and concave surfaces of the hardened steel mold.Firstly,a model for adaptive sampling of convex-concave surfaces is established,and then the convex-concave surface is divided into triangular meshes based on the improved wavefront method to obtain adaptive triangular mesh sampling points.In the area where the curvature of the convex-concave surface mold changes greatly,the sampling points are relatively dense,otherwise,they are relatively sparse.After the mesh is divided,the quality of the mesh is evaluated,and the mesh quality is better than the surface mesh obtained by the Delaunay triangular meshing method.Then,the mold surface is reconstructed based on the T-spline control points.According to the point cloud data obtained by adaptive triangular mesh sampling,the octree method is used to partition the point cloud data and map it to a twodimensional plane,and the surface mesh control points are adjusted through iterative operations.Then use the wavelet decomposition method to optimize the internal control vertices to construct the T-spline mold surface.Finally,the error evaluation of the mold surface based on the T-spline control point reconstruction is carried out.Since the object of this study is the machining error of hardened steel convex and concave curved surfaces,the method of surface profile error is selected for error analysis in the process of error evaluation.The experimental plan is compared with the mold surface reconstructed by the sampling data on the coordinate measuring machine to verify the accuracy and stability of the on-machine measurement plan.