Research On Tool Path Generation And CAM Implementation In CNC Machining Of Denture

During the traditional production process of oral repair,almost every procedure involves manual operation.Therefore,its denture manufacturing cycle is long,precision is difficult to ensure.Since the end of the 20 th century,CAD/CAM technology has been widely used in the design,processing and manufacturing of oral prostheses.CAD technology mainly uses computer technology and digital image processing technology to assist the design of restoration.In CAM,the numerical control code is generated by software calculation,and then the machine tool is controlled for the molding of the prosthesis.Compared with the traditional method,the digital oral prosthesis CAD/CAM technology has a higher degree of automation,and the prosthesis with high quality can be obtained within 1 hour.This paper mainly studies the strategy of tool path generation and the realization of CAM algorithm in CNC machining of oral prosthesis.The main goal of this project is to generate smooth and continuous tool trajectories with high machining efficiency for rough machining and finishing machining of repair body.The tool path generation algorithm of this paper is implemented by C++ program,Specific research contents are as follows:(1)Geometric topology information modeling of triangular mesh surface model.In order to facilitate the following tool path planning,the grid surface was reconstructed with half-edge data structure and redundant vertex information was removed.For the condition of discrete normal vector and curvature information of grid surface,introducing a shape area weighting method to estimate the normal vector of contact point,based on the least square principle to locally quadratic fitting of meshes,relevant differential geometry information can be obtained.(2)Tool path generation and post-processing of restoration.on the basis of the molar crown restoration as the research object,in the rough machining tool path generation,with the improved cutting plane method,make full use of the topological neighborhood information of grid surface,has improved the efficiency of the solution of the tool path.In the fine machining tool path generation,based on the harmonic mapping theory,the initial single-loop spiral path was generated by using the equal-parameter loop helical method,and the iterative calculation was carried out by the Scallop height method,and the smooth and continuous Scallop height spiral path with higher machining efficiency was finally generated.At the same time,in the above mentioned tool path generation process,it is necessary to carry out self-intersection,interference and redundancy post-processing to ensure the generated tool path has good machining performance.(3)Tool path planning software development and processing experimental verification.In Qt development environment,the main functional modules of DentalCAM,a tool path planning software,were developed.At the same time,this paper compares and analyzes the tool path generation algorithm and WorkNC software in computing time and processing efficiency,and verifies the feasibility and effectiveness of this method through experiments.The results show that the method can improve the processing efficiency as much as possible on the premise of guaranteeing the surface quality.The obtained molar crowns can meet the needs of clinical application of oral prosthesis.