Research On The Design And Optimization Of Self-supporting Porous Structures Inside 3D Printing Models

Fused deposition modeling(FDM)3D printing technology,as a kind of rapid prototyping technology,has a relatively long research history in the field of additive manufacturing,so it is used widely.As the same time,desktop-level FDM 3D printers are favored by academia and industry due to its simple operation and relatively low price.The lightweight design has always been a research hotspot of 3D printing,and the optimization of the internal support and filling structure is priority.For FDM,the internal support structure not only causes a waste of materials,but also increases the printing time,which seriously affects the molding efficiency of 3D printing.Different scholars have proposed different solutions to this,and many lightweight structures have emerged.Although many structures can replace the original dense filling structure,they cannot eliminate internal support structures.Although some methods can generate selfsupporting or less-supported filling structures,the material saving effect is not obvious.Therefore,from the perspective of lightweight,this article proposes an internal selfsupporting porous structure optimization design method,which includes two major aspects: preprocessing includes model uniform offsetting,offset model layering and offset model block and the optimization design of the inner self-supporting porous structure consists of generating the shrinkage direction by Voronoi diagram and calculating shrinkage distance by the particle swarm algorithm.The main work content is as follows:(1)Preprocessing of 3D printing model,which is mainly divided into the following three parts:(1.1)Mesh model offsetting.The offset model is obtained by offsetting the vertices of the model along the direction of the normal vector of the vertex.The mesh model offsetting is mainly to ensure that the printed model has a certain initial thickness,provide a margin for subsequent processing,and avoid affecting the external surface quality of the mesh model during subsequent processing.(1.2)Offset model layering.The offset model is intercepted by the cutting plane of height z to obtain a series of parallel slice contours.The layering of the offset model can not only provide a basis for model block,but also affect the shrinkage direction of the reconstructed surface vertices.By determining the appropriate thickness of layers,the slice contour grouping can be more reasonable.(1.3)Offset model block.The grouping rules of slice contours are proposed,and all slice contours are clustered into corresponding groups;a triangulation algorithm is proposed to reconstruct the contour group to complete the offset model block.Offset model block simplifies the model and reduces the difficulty of the algorithm.(2)Optimized design of self-supporting porous structure.In this paper,the selfsupporting porous structure is formed based on the uneven shrinkage of the vertices of the slice contour.Through the Voronoi diagram generated by the vertices of the slice contour,the shrinkage direction calculation and the uppermost slice degradation are based on the poles of the Voronoi diagram;the block is used as a unit,and the optimization model of the self-supporting porous structure is established according to the surface constraint,the edge constraint and the geometric constraint;Volume maximization is the goal to be optimized through particle swarm optimization.The innovations of this thesis:(1)Based on the layer contour,this paper proposes a method of generating inner self-supporting porous structure based on particle swarm algorithm;(2)It proposes a method to extract the skeleton line based on the Voronoi diagram to degenerate the uppermost slice contour.