RP网络化制造中STL文件传输的实现

在RP网络化制造中,STL文件应快速稳定地由远端计算机传输到快速原型机上,而STL文件数据量非常大,不易于传输。因此,采用多线程技术和Winsock网络编程接口,在VC 6.0环境下编写了应用程序,成功实现了STL文件的传输。     

基于VC和OpenGL的STL文件的分层和显示

STL文件是快速成型系统的标准文件类型,广泛应用于数控加工、逆向工程和有限元分析等.详细介绍了STL文件的读取和分层算法,并利用VC＋＋6.0平台结合OpenGL编程技术,实现了STL文件格式的读取、分层算法以及STL模型的三维显示、视角变换、缩放、平移和分层显示等功能.为进一步实现数控系统直接使用STL文件进行加工奠定了基础.     

Parasolid数据的STL变换研究

为满足CAD软件与快速成形领域的数据交换需要,提出了一种Parasolid数据的STL变换方法。利用Parasolid建模核心的PK-TOPOL-facet()函数将Parasolid模型按STL文件规则进行三角网格化,通过返回的拓扑信息构建三角面片与它的顶点和法向量的拓扑关系,并由此生成了STL文件。应用实例和Solidworks软件诊断表明,采用该方法可以将Parasolid文件变换为STL文件,生成的STL模型中无错误面和缝隙存在。     

Re-triangulation in STL meshes for rapid prototyping and manufacture

The main objective of this research is to identify ways to simplify the STL meshes, while simultaneously maintaining the accuracy of the STL file. It demonstrates a technique to simplify large and complex STL triangular meshes and to optimise STL shape for rapid prototyping and manufacture. STL mesh re-triangulation can be separated into two processes, i.e., mesh deletion and mesh rearrangement. In the mesh deletion process, two kinds of weighted-value ratio algorithms can be chosen for determining the suitable value of STL mesh deletion. A genetic algorithm that incorporated fitness functions was used for the optimisation of the rearranged STL meshes. Two case studies of STL mesh reconstruction, which examine the effects of the algorithms, are presented. These studies show that optimisation of the shape of the STL file reduces its size, resulting in a reduction of the fabrication time and improvement of the rapid prototyping process.     

An Effective Error-Tolerance Slicing Algorithm for STL Files

Although the STL (stereo lithography) file format is the de facto standard for the rapid prototyping industries, there are always some defects in STL files, many of which are difficult to correct. Instead of correcting the defects of bad STL files by a manual, interactive and complex approach with an STL file correction program, an error-tolerance slicing algorithm for STL files is proposed in this paper. With the detailed analysis of complex defects such as cracks and non-manifold facets, a complete topological structure for the facets model with defects is built and the layer is sliced effectively. The badly sliced contour is processed by crack-tracking and non-manifold facet travelling methods to obtain a correct contour in a relatively easy 2D way.     

选区电化学沉积快速成型轨迹规划

数控选区电化学沉积快速成型是将快速成型技术与电化学沉积技术相结合的一种新型快速成型方法。为保证数控选区电化学沉积快速成型的零件精度,提出了一种基于电化学沉积技术的快速成型工艺的路径生成算法。结合该成型工艺的特点,分析了快速成型领域常用的几种扫描方式,轨迹规划方案分为STL切片处理、轮廓偏置、轮廓填充、数控加工代码生成四个过程,提出了平行交错往复间隙填充法。实验表明该轨迹规划能够达到选区电化学沉积快速成型的要求,制造出高精度、高表明光洁度的零件。     

Machine path generation using direct slicing from design-by-feature solid model for rapid prototyping

This paper explains a new machine path generating system that its output is compatible with different rapid prototyping processes. The basis of this system is direct slicing from design-by-feature solid model. Slicing a computer-aided design (CAD) model through intersecting the model with the XY-plane at each Z increment is a well-known method of path generation. Slicing a CAD model is currently conducted through stereolithography (STL) file slicing, direct slicing, and additive direct slicing. A direct slicing approach inside a design-by-feature solid modeler is proposed. Autodesk Inventor solid modeler, as a design-by-feature solid modeler, is used for 3D solid modeling. The proposed system is implemented by Visual Basic codes inside Inventor. In this approach, first protrusion and subtractive features that form a model are extracted. Then, the intersection of each feature and the XY-plane is identified. Then, the internal and external loops are found. Depending on the specific rapid prototyping (RP) process requirements, internal or external hatch are also computed, respectively. Finally, a continuous path in required format is generated. The system reported in this paper has been successfully tested on several complex 3D models created in Inventor. The system offers customized output for different RP processes that need external or internal hatch pattern. The proposed approach for generating RP machine path through feature recognition inside design-by-feature solid modeler overcomes with the problems that are caused by imperfect STL files. Also, this system is capable of generating code compatible with major rapid prototyping processes.     

STL模型的分层轮廓数据优化算法

在快速成形系统中 ,由于STL模型在切片后的截面轮廓数据含有大量的数据冗余点 ,严重影响了插补加工的精度和效率。为此 ,作者提出了一种数据冗余点的联合剔除算法 ,在保证加工精度的条件下 ,以进一步提高加工效率与质量     

Integration of RP and explicit dynamic FEM for the visualization of the sheet metal forming process

This paper develops a FORTRAN program to convert the explicit dynamic finite element method (FEM)-simulated deformed sheet to the stereolithography (STL) format used in the rapid prototyping (RP) apparatus. Such integration of the RP/FEM can rapidly produce a visualized 3D physical part of the sheet deformation state. Three cases – cylindrical drawing, bore expanding and square cup drawing processes, simulated by explicit dynamic FEM – were investigated to verify the integration system. The wrinkled flange in the cylindrical drawing process, the circle hole expansion in the bore expanding process, and the square cup in the square cup drawing were successfully predicted by explicit dynamic FEM, and the rapid prototyping 3D physical parts also showed good visualization of the deformed sheet for the above three cases. It proves that the integration system of RP/FEM will be able to supply a useful method for the visualization of the 3D physical part in the sheet metal forming process.     

Enhanced STL

STL format is widely used as a de facto industry standard in the rapid prototyping industry due to its simplicity and robustness. However, on account of its shortcomings and inadequacy in applications, many interface alternatives have been brought forward. In this paper, a new scheme is proposed to enhance the approximation accuracy and to extend functions of STL by means of introducing additional feature and attribute codes into STL format. The geometry feature code describes a tetrahedron based on the STL triangular facet, which provides better approximation to the object surface covering. The attribute code attaches attributes of object surfaces such as colours and markers to STL triangular facets. Moreover, the enhanced STL also shares the structure of binary STL format by filling feature and attribute codes into its blanks, and therefore is compatible with STL. Compared with STL, the enhanced STL provides not only higher accuracy with the same file size and compatible format, but also colour and marker functions for rapid prototyping.     

快速成型中封闭PS曲线边界补偿重建算法研究

对快速成型数据处理中封闭PS边界曲线补偿重建算法进行了研究,分析了已有的几种PS边界曲线补偿重建算法的特点。根据快速成型数据处理过程中截面多边形补偿的特点,提出了基于有效交叉点搜索的补偿边界重建的新算法;并在已开发的RP数据处理软件中成功应用,提高了该数据处理软件的稳定性。     

基于STL文件的实体分割算法研究

由于快速成型机加工尺寸的限制,难于制造尺寸较大的零件。针对这一问题本文提出一种基于STL文件格 式的实体分割算法,对STL文件分割过程中的关键问题进行了详细地论述,包括:截面轮廓的生成,截交三角面片的 处理和截面轮廓的三角化算法;通过对STL文件的分割处理,提高了快速成型系统对大尺寸零件的制造能力。     

海量STL文件的快速读取与显示

STL文件作为一种通用的三维数据文件格式,广泛应用于快速成型及其他领域。如何快速读取海量数据的STL文件并显示,是模型后续操作的一个首要环节。本文针对海量数据的特点,采用内存映射手段、基于哈希表结构的冗余顶点删除和OpenGL中显示列表技术等,对海量STL文件的快速读取和显示进行了研究,并和国外先进软件进行了比较,实验数据表明本文方法较Surfacer软件和Rap idForm软件提高效率25%~40%左右。     

自由曲面的反求工程与快速原形技术

反求工程与ＲＰ技术相结合的可以为快速产品开发提供关键技术技术;数据获取技术和曲面重建技术。本文首先对这两方面的关键技术的原理与方法进行了分析;然后分析了ＲＰ机驱动数据文件－ＳＴＬ文件格式。提出了不经过格式转换,直接从ＣＡＤ模型以ＳＴＥＰ或ＳＴＬ格式进行切片处理来研究如何提高精度的新思路。     

激光熔敷快速制造技术及其精度保证分析

RP技术在当今市场上有较强的优越性。本文分析了快速成型系统的成型原理;重点分析了一种新型激光熔敷快速成型系统;介绍了STL格式模型和利用RP技术的快速性和铸造工艺的成熟性制造功能性产品的CAE系统;并构建了多回路误差控制及反馈系统,从而保证系统的精度。     

复合快速成形中基于STL模型的分层研究

研究了面向分层实体制造与数控铣削复合成形的基于STL模型的三维层生成算法。利用凹边在上下两个方向上的可见性确定分层位置,通过切割平面与各三角面片求交实现STL模型的分割,并把分割面三角网格化生成封闭的三维层。分层的结果可满足复合快速成形工艺要求。     

基于STL文件的变密度三维全六面体网格自动生成方法

针对STL文件在传递复杂几何实体模型信息方面具有精度较高的特点，提出了一种基于STL文件变密度三维全六面体网格自动生成方法，给出了STL文件的数据格式及其内容约定，详细阐述了基于STL文件空间CAE模型表面特征自动识别、拓扑关系的生成和变密度栅格法加密信息场的建立等关键技术。实现了在实体模型表面曲率较大和厚度较小的局部区域进行协调加密，可以获得与实体模型边界吻合良好的全六面体协调网格，适合于工程问题的有限元分析计算。若干复杂实体模型算例表明，该算法实用性强，效果良好。     

三角Bézier曲面建模的RE系统与RP系统集成

为解决复合三角Bezier曲面与快速原型系统接口,以便实现两者集成,提出了按给定精度从复合三角Bezier曲面模型产生STL文件数据的方法,并在原型系统上得到验证,将推动反求工程与快速原型技术的进一步应用。