Research On Key Technologies Of 3D Printing Virtual Simulation Teaching System

In recent years,with the coming of "the third industrial revolution",3D printing technology has been widely applied in all walks of life,and those who master the 3D printing technology are more valued.So,many schools at all levels add 3D printing courses to cultivate the related talents to meet the demands of the society.However,during the process of 3D printing teaching and learning,some problems,such as slow printing speed,high printing cost,low printing success rate and hard printer maintenance,and the like,caused by hardware and software technology limitations,cannot be avoided.By analyzing and summarizing the problems above,we find that the technical limitations in 3D printing can be broken from two aspects.On the one hand,applying some simulation methods to evaluate and optimize virtual printed models to improve model quality and printing success rate;on the other hand,using some 3D visualization technologies to show 3D printing process to break the time and space constraints and reduce the teaching cost.Accordingly,we study the key technology of 3D printing virtual simulation teaching system from the perspective of technological innovation and teaching application in this paper.Firstly,we calculate the main properties of printed models,such as volume,height of barycenter,distance of being easy to dump,stability and so on.We also simulate the static pressure tests of printed models based on the finite element method.To support the two works,we propose an adaptive tetrahedral mesh generation algorithm based on density field.The algorithm can generate tetrahedral meshes of size-adaptive cells by optimally dividing the interior space of a 3D model based on the dual relationship between Centroidal Voronoi Tessellation and Delaunay triangular mesh.Secondly,we propose a scheme based on the depth-peeling technique and the pattern search algorithm to optimize the orientation of the printed models and generate the corresponding support structures.There are two innovations in this scheme:one is that the fragments information of printed models obtained by depth-peeling is utilized to calculate the overhanging areas of the models;the other is that a dual objective optimization function about overhanging area and support volume and a two-step process are adopted to determine the optimal orientations of printed models.Thirdly,we propose three kinds of interior structure modeling methods to optimize the interior spaces of printed models.Based on Centroidal Voronoi Tessellation,3D implicit function and spatial recursive subdivision respectively,the three methods can create triangular cone-like frame,single-gyroid frame and grid frame.Finally,we parse the Gcode files of printed models to synchronously visualize the slice,path planning and manufacture processes of the models on the basis of the advanced 3D graphics rendering libraries.The experiments and teaching application cases show that our study works are not only technically advanced,but also boost the effect of teaching and learning in 3D printing course.As far as technology is concerned,our tetrahedral mesh generation algorithm can quickly generate cell-size adaptive high-quality tetrahedral meshes,which can be applied in properties calculation and finite element analysis;our orientation optimization method is able to obtain the optimal orientation of a printed model under the different weights of overhanging area and support volume;three interior frames designed by us all have the characteristics of small volume and high physical strength,besides,the single-gyroid frame and grid frame are self-supporting;our visual simulation can show the 3D printing process and pre-processing flexibly,clearly and synchronously.In the aspect of teaching and learning,the ability of calculating the main properties of 3D printed models of our methods can help students design better 3D models,and assist teachers to objectively evaluate the quality of the models designed by their students;our orientation optimization and support generation method can choose the suitable orientations of printed models for students to effectively reduce the material consumption of support structures and improve the surface quality of the models;our three interior structure optimization methods can evidently cut down the consumption of printing material and printing time,so that 3D printing course teachers can flexibly carry out their teaching activities;our visual simulation of 3D printing process and pre-processing allows students to experience and understand the real printing process in a virtual environment.At the end of this paper,we summarize our study on the key technology of 3D printing virtual simulation teaching system and plan our tasks in future.