基于STL模型的冰模快速成型切片算法研究

发布时间：2018-08-13 21:23

【摘要】：基于冰模的熔模铸造是一种用冰模代替蜡模、白模等消失模的熔模铸造工艺,具有高精度、低成本、无污染以及工艺控制要求降低等特点。获取冰模的传统方法需要制作硅橡胶模具,但是硅橡胶模具制作工艺复杂、生产周期长及成本高,适合于大、中批量的铸造生产需要。为快速制作高精度的冰模,满足小批量、个性化的铸造生产需要,本课题组利用快速成型技术(RPM)制作冰模——冰模快速成型技术,其本质上属于FDM技术,区别在于所用材料、成型条件不同。尽管快速成型制造的工艺方法有多种,但是获取模型的二维轮廓数据仍然是快速成型制造的第一步,因此对切片处理技术研究是一项重要任务。为实现与本课题组搭建的冰模快速成型实验系统配套使用的STL模型数据处理软件,提出一种基于动态空间索引的分组切片算法,并基于该算法开发切片软件原型系统。本文的主要研究内容如下:(1)对冰模快速成型切片算法进行基础研究。对三类现有基于STL模型的切片算法进行深入分析,并给出每类算法的原理、算法实现基本流程与每类算法的优缺点;根据冰模成型特点,对冰模快速成型切片算法需求进行分析。(2)提出一种基于动态空间索引的分组切片算法。利用Kd树构建STL模型顶点索引,去除模型中的冗余顶点,基于半边结构重建STL模型的全局拓扑关系,将能表示半边结构的出射半边融合到Kd树的叶节点。基于STL模型中的三角面片在切片方向具有的位置特征,对所有三角面片进行分组,利用Kd树与半边结构相融合的空间索引对分组后的面片快速计算每组的有序三角面片集合。通过对模型构建全局拓扑关系,不仅能减少对每组三角面片构建局部拓扑结构的时间,同时利用Kd树高效的查询性能以及半边结构存储的拓扑关系,从而大大提高切片的处理效率。(3)开发冰模快速成型切片软件原型系统。通过对切片软件原型系统进行功能需求分析,确定软件整体设计方案。采用模块化的设计方法对软件进行模块划分并明确各模块的功能,以本文提出的切片算法为核心算法,利用图形界面应用程序开发框架Qt和OpenGL技术实现切片软件原型系统。本文主要目的是开发适用于同课题组搭建的冰模快速成型实验系统的切片软件原型系统。通过吸收现有切片算法的优点,提出基于动态空间索引的分组切片算法,并基于Qt和OpenGL实现了切片软件原型系统。对本文提出的切片算法及切片软件原型系统分别进行了实例验证。结果表明,本文切片算法稳定可行,实现对STL模型进行高效率切片,切片软件原型系统实现了预期的功能,能对模型进行辅助变换、多视角观察模型、显示每层切片轮廓图形等功能。
[Abstract]:Investment casting based on ice mold is a kind of lost pattern casting technology, which uses ice mold instead of wax mold and white mold. It has the characteristics of high precision, low cost, no pollution and low requirement of process control. The traditional method of obtaining ice mold needs to make silicone rubber mould, but the process of making silicone rubber mould is complicated, the production cycle is long and the cost is high, which is suitable for large and medium batch casting production. In order to quickly make high precision ice mold and meet the needs of small batch and individualized casting production, our research group uses rapid prototyping technology (RPM) to make ice mold -ice mold rapid prototyping technology, which is essentially a FDM technology, which is different from the material used. The molding conditions are different. Although there are many process methods for rapid prototyping, the acquisition of 2D contour data is still the first step of rapid prototyping, so the research of slice processing is an important task. In order to implement the STL model data processing software which is used in the ice mold rapid prototyping experiment system built by our team, a grouping slicing algorithm based on dynamic spatial index is proposed, and a prototype slicing software system based on this algorithm is developed. The main contents of this paper are as follows: (1) the basic research of ice mold rapid prototyping slicing algorithm. Three existing slicing algorithms based on STL model are analyzed in depth, and the principle of each algorithm is given, the basic flow of the algorithm and the advantages and disadvantages of each algorithm are given. The requirements of ice mold rapid prototyping slicing algorithm are analyzed. (2) A grouping slicing algorithm based on dynamic spatial index is proposed. The vertex index of STL model is constructed by using KD tree, the redundant vertices in the model are removed, and the global topological relation of STL model is reconstructed based on the half-edge structure. The outcast half-edge of the half-edge structure is fused to the leaf node of the KD tree. Based on the position characteristics of triangles in the STL model, all triangles are grouped, and the ordered triangulation sets of each group are quickly calculated by using the spatial index of KD tree and half-edge structure. By constructing the global topological relation of the model, not only the time of constructing local topology for each group of triangular patches can be reduced, but also the efficient query performance of KD tree and the topological relation of half edge structure storage can be used. Therefore, the processing efficiency of slicing is greatly improved. (3) A prototype software system of ice mold rapid prototyping slicing is developed. By analyzing the functional requirements of the slicing software prototype system, the overall software design scheme is determined. The modular design method is used to divide the software modules and the functions of each module are defined. The slicing algorithm proposed in this paper is taken as the core algorithm and the graphical interface application development framework QT and OpenGL technology are used to realize the slicing software prototype system. The main purpose of this paper is to develop the slicing software prototype system which is suitable for the ice mold rapid prototyping experiment system built by the same research group. By absorbing the advantages of existing slicing algorithms, a grouping slicing algorithm based on dynamic spatial index is proposed, and the slicing software prototype system is implemented based on QT and OpenGL. Examples of slicing algorithm and slicing software prototype system are given. The results show that the slicing algorithm is stable and feasible, the STL model can be sliced efficiently, the prototype system of slicing software realizes the expected function, it can transform the model and observe the model from many angles of view. Display each layer slice outline graphics and other functions.
【学位授予单位】：山东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG249.5;TP311.52

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