Research On Direct Layering Algorithms Of Point Cloud Models Based On Surface

The key problem of the direct stratification algorithm based on point cloud is the acquisition of the stratified contour points and the fitting of the stratified contour in additive manufacturing,which directly affects the stratification precision of the algorithm and further affects the forming precision of additive manufacturing technology,and how to balance the contradiction between precision and efficiency is also the focus of the research.Through a lot of literature investigation and analysis,this paper carried out an in-depth study on the key and difficult issues of point cloud model slice in additive manufacturing:(1)The ordinary intersecting method obtains contour points by direct connection of straight lines,which has some problems of precision loss,and the obtained contour points are too messy.In this paper,the curved surface based slicing method is used to improve the layering accuracy:In order to reduce the problem of surface fitting deviation,the domain point set was retrieved by establishing kd-tree and balancing domain.and through the field point set adopts the method of weighted least square method to fit quadric surface,at the same time through the selected points and normal vector,slicing plane normal vector using the point of French for intersecting planes,then conicoid and intersecting plane intersection,intersecting line available,The hierarchical contour point set can be obtained by intersecting the intersection line and the slice plane.A method of "clustering + sorting" is proposed to solve the problem of multiple contours.Finally,different models were used to analyze the hierarchical effect and efficiency of the proposed algorithm,and the same model with different points was used to verify the robustness of the proposed algorithm in the aspect of noise.The experimental results show that the proposed algorithm has high slicing accuracy,wide applicability and robustness in the aspect of noise.(2)Due to the characteristic of additive manufacturing layer by layer,it is inevitable to produce ladder effect in the molding process.The usual solution is to adopt a smaller layer thickness in the iso-thick slicing algorithm,which can reduce the ladder effect to some extent but increase the slicing time.In this paper,based on the above algorithm,an adaptive hierarchical algorithm is proposed.The main idea is: to establish the polygon of hierarchical contour and Boolean operation on two adjacent polygons,and then by comparing the threshold value,the smaller layer thickness is used in the place where the model contour changes greatly,so as to achieve adaptive hierarchical.Finally,the adaptive hierarchical experiment is carried out by using multiple models,and the results show that the algorithm can reduce the ladder effect to a certain extent,and has good hierarchical effect and stability.(3)Due to the clutter of point cloud data or the influence of noise points,when extracting hierarchical contour points in hierarchical algorithm,the contour points may be sparse or missing.Aiming at this special situation,this paper proposes a contour point interpolation method,which is based on the nearest correlation point pair of the contour gap,and uses the method of directly intersecting with the tangent plane to obtain the interpolation points.Through the layered processing experiment of the model,it is verified that the algorithm can obtain more dense layered contour points with certain accuracy.Finally,the feasibility of the above algorithm is verified through FDM 3D printing experiments,comparing the advantages of additive manufacturing midpoint cloud model with STL model slice,The main content,innovation and shortcomings of this study are summarized,and part of the future research directions are pointed out,which provides reliable reference value for the further study of scattered point cloud layered algorithm.