Research On The Tool Path Generation For Partition Machining Of Complex Triangular Mesh Model

In recent years, application of triangular mesh model is increasingly widespread.Moreover, the research on CNC machining for triangular mesh model has beengrowing to be concerned. However, researches on the tool path generation fortriangular mesh model are insufficient, and tool paths on the model were mostlygenerated by a single method of tool path generation. That never meets the machiningrequirement of complex model. Therefore, the method of partition machining waspresented to solve the contradiction between machining efficiency and accuracy inCNC machining of the complex triangular mesh model, which is composed of thesegmentation of mesh model and tool paths generation of sub-regions. According tothe research contents, the following research works are carried out in this paper.Firstly, to seek the adjacency of mesh elements (vertices, edges, facets) andcalculate the amount of differential geometry of model quickly, topological structureof the triangular mesh model based on half-edge data structure was established.Moreover, the calculation methods of normal vector, curvature and dihedral angle formesh model surface were introduced, and the selection method of neighbor point inR-radius was proposed.Secondly, triangular mesh model was divided into sub-regions for machining. Inthis step, the complex triangular mesh model was classified as model with clearboundary and model with unclear boundary. Then, growing principle based ondihedral angle was proposed for the region growing segmentation of model with clearboundary, and growing principle based on machining feature formulation waspresented for model with unclear boundary. To avoid unnecessary short tool path,sub-regions were optimized, and their boundaries were smoothed.Finally, different tool path planning methods were adopted for different featuresub-regions. The tool path of flat feature surface was planned with iso-planar method.And the iso-scallop method was adopted for the tool path generation from fluctuantfeature surface. To generate constant scallop-height tool paths from the sub-regions with irregular boundary, the method of projection and offset was improved. Theimprovements are composed of three aspects: the method of original tool pathgeneration, the process of tool path projection and offset, the processing method oftool path on feature sub-region boundary.In this thesis, C++programming language was used for implementation of thealgorithms. The instances illustrated the validity of the algorithms in this paper. Themain innovations of the thesis are as follows:(1) The tool axis vector is considered asan influencing factor of growing principle, so that the sub-regions have the machiningcharacteristics;(2) The growing principle based on surface machining characteristicsis proposed to divide triangular mesh model into different machining feature regions;(3) To generate constant scallop-height tool path from the sub-regions with irregularboundary, the method of projection and offset is improved.