Research On Compound Surfaces Model Repair And Based On Repaired Compound Surfaces Offset Algorithm

In NC machining,a good surface model can generate tool path satisfying quality requirements.However,defects located in the model are often caused by data loss during file exchange,and these defects affect the generation of tool path.Therefore,it is necessary to repair the defects in the model.However,in tool path planning,there are still some unsmooth paths which are generated based on the repaired model,so this paper proposes a method to improve the tool path quality by using surface offset based on the repaired model.This method has important theoretical significance and practical value,including two parts.(1)For the problem of repairing combined surfaces,this paper proposes an automatic repair method for surface models based on defect recognition.By constructing topology information of the surface model,the area to be repaired is identified according to the topology information.For the areas that need to be repaired,a strategy of “sewing” after “cutting” is proposed.In view of the defects that still exist after the sewing,an algorithm was proposed to identify the untrimmed area on the model and repair the defect area.Finally,the repaired combined surface model was obtained.(2)For the offset problem of combined surfaces,this paper proposes a biasing method based on triangular mesh model.The surface model is first discretized into a primitive triangular mesh model.The triangular mesh model is preprocessed to obtain the normal vector of the corresponding mesh point,and the triangular mesh is divided into continuous and discontinuous areas according to the normal vector.For non-consecutive areas,a method for detecting self-intersecting parts is proposed.Then the self-intersecting part is removed from the original triangular mesh model.In order to avoid gaps in the offset region,a new grid point is inserted into the gap region of the original triangle mesh model and a triangle grid filling method is proposed.Finally,an offset triangle mesh model is obtained.The method of repairing the combined surface model proposed in this paper can ensure that the repaired surface model and the pre-repaired surface model avoid distortion,and the repaired surface model satisfies G0 continuity and can be applied to subsequent software processing.The method of biasing the repaired combined surface model proposed in this paper can realize the offset of the surface with large curvature change,ensure that the offset triangle mesh model does not have self-intersection and void area,and the quality of the triangular mesh model is better.Well,it can be applied to subsequent toolpath generation.The above stated algorithm is based on the existing CAM software as a platform,and the algorithm process is implemented using C++ language.The reliability of the algorithm is verified by using an example.