Research On Tool Path Planning Method Of Denture Machining Based On Triangular Mesh Model

Our country has a large population and a high demand for denture.In order to improve the accuracy of denture processing,the tool path trajectory of denture needs to be planned in the process of denture CNC machining.For this purpose,this thesis conducts an in-depth study on the tool path trajectory generation algorithm of denture triangular mesh model,focusing on the bias algorithm,tool position point generation algorithm and curve interpolation algorithm,and further develops the denture tool path trajectory generation system.In the offset algorithm,the data in the triangular mesh model is reconstructed using the topological reconstruction algorithm based on the triangular mesh model file rules,and the data model is simplified in order to facilitate the subsequent tool path trajectory generation.The vertex offset algorithm is studied in depth,and it is found that the current vertex offset algorithm has the problem of insufficient offset distance,which is easy to cause over cutting of the NC machine tool.For this reason,the vertex offset compensation algorithm is proposed to compensate for the insufficient distance.In order to verify the effectiveness of the algorithm,the denture mesh model is used for practical verification,and the results show that the vertex offset compensation algorithm proposed in this thesis can effectively reduce the bias error of the triangular mesh model after offsetting.In the tool location generation algorithm,the row spacing formula of tool path is calculated.In order to get tool location,an intersection method of section plane is proposed according to the tool selection and cutting mode,which is based on the offset model built previously.Besides,a position relationship between section plane and triangular mesh model is also classified,and a tool position coordinates calculation method of is deduced.In order to reduce the calculation time of tool location,an tool location generation algorithm based on topology structure is proposed.In addition,the incremental method in 3D printing is used to reduce the time complexity of the intersection method of cross-section planes,and the fast calculation of tool position coordinates is realized.In view of the problem that redundant cutter sites will lead to the decline of denture quality,this thesis uses non redundant cutter sites optimization algorithm to remove redundant cutter sites,which can effectively improve the quality of denture.In the curve interpolation algorithm,the cubic non-uniform B-spline curve interpolation algorithm is used to interpolate the cutter position,and the smooth cutter path of the denture triangular mesh model is generated.The isoparametric linear approximation method is used to calculate the coordinates of the interpolation points and obtain the cutter motion coordinates.Based on the above research,this thesis develops a denture tool path trajectory generation system in Python environment,including the main functions of bias model,tool position point generation and tool path trajectory generation,etc.This system can read the denture triangular mesh model and output the tool motion coordinates,and realize the tool path trajectory planning of denture CNC machining CAM system.The system is easy to use and has a friendly interface.The user only needs to input the tool radius and row spacing to automatically generate the denture tool path trajectory to further automate the denture machining.