B-spline surface reconstruction and direct slicing from point clouds

The issue of surface reconstruction and slicing from point clouds has been receiving extensive attention recently. When using the B-spline surface fitting technique, the difficulty of parameterization exists. At the same time, for interfacing between reverse engineering and rapid prototyping, the point clouds are usually converted to an stereolithography (STL) model. This leads to a huge file size and requires expert modeling skills. The objective of this work is to establish a base surface parameterization and direct slicing strategy for scattered data based on a cross-sectional design technique. We first present a new method of directly extracting sectional contours from point clouds. Then, we create a base surface by skinning the primary boundary curves and interior sectional curves. Based on a good parameterization, the final surface is achieved with tight tolerance. Several practical examples have demonstrated the feasibility of the proposed method. It can be widely used in Number Control (NC) machining and rapid prototyping.     

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。     

离散数据直接映射STL数据文件

在研究反求工程的输出接口与快速成型输入接口标准与技术的基础上,提出了利用离散数据直接三角剖分,实现STL文件格式方法,并给出具体案例,成功的解决了RE／RP系统数据集成的问题。     

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.     

基于自由曲面点云的快速原型制作技术研究

针对不附加任何拓扑和几何信息的云状数据三维重建问题,提出了对点云直接进行分层处理快速制作原型的新方法。在对点集进行空间结构划分的基础上,采用最小距离关联点对方法提取层面轮廓线数据,并对其加以匀化和精整从而直接生成快速成形机的层片接口文件,避免了常规方法存在的耗时和需要很高的造型技巧等不足,而且片面的错误校验与修补等繁琐工作也将不再进行,提高了快速成形前处理的效率,非常适合分层实体制造(LOM)等成形工艺。     

Shape reconstruction, shape manipulation, and direct generation of input data from point clouds for rapid prototyping

Shape reconstruction from point clouds has received considerable attention in recent years on account of its ability to directly integrate reverse engineering with rapid prototyping. The primary objective of this study is to develop an integrated system that enables one to generate input data for rapid prototyping by constructing complete shape models from point clouds obtained with various measuring devices, including laser scanners, digitizers, and coordinate-measuring machines. We first present a novel approach to reconstructing a shape from point clouds based on implicit surface interpolation combined with domain decomposition. We then propose various related algorithms for generating input data for rapid prototyping, ranging from shape manipulation to complete solid generation. The validity of this new technique is demonstrated for a variety of point clouds with differing degrees of complexity.     

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。     

逆向工程与快速成型技术的应用

介绍了逆向工程技术和快速成型技术的定义和逆向工程与快速成型的一般流程。并通过一个简单球面的反求工艺实例,阐述了逆向工程中数据采集、产品建模以及产品快速成型的一般过程。从而证明了逆向工程技术是一个多领域、多学科的系统工程,是基于新的设计思想和方法,在计算机技术、数控测量技术和CAD/CAM技术发展基础上产生的一项新技术,能广泛运用于模具行业,并有一定的影响力。本文证实了逆向工程技术和快速成型技术的前沿性和可靠性,并展望了逆向工程技术与快速成型应用的前景。     

STL File Generation with Data Reduction by the Delaunay Triangulation Method in Reverse Engineering

Reverse engineering has been widely used for the shape reconstruction of an object without CAD data and typical steps include the scanning of a clay or wood model and the generation of manufacturing data such as an STL file. A new approach to remove point data with Delaunay triangulation is introduced to deal with the size problems of the STL file and the difficulties in the operation of the rapid prototyping (RP) process. The selection of a group of triangles, based on the angle, is used for a robust and reliable implementation of the Delaunay triangulation method. The developed software enables the user to specify the criteria for the selection of the group of triangles by the angle between triangles, the percentage of reduced triangles, and the allowable area. This approach can be used to reduce the measuring data from the laser scanner, thus save the handling time of point data during the modelling process and is useful for verifying and slicing the STL model during the RP process.     

面向快速原型制造的逆求技术

逆求技术是一种应用非常广泛的新兴技术,在快速原型制造中具有重要作用。本文介绍了面向快速原型制造的逆求工程系统的结构体系、测量方法以及相应的数据处理手段,并指出了存在的问题和今后的发展方向。     

逆向工程曲面构建与快速成型

逆向工程与快速成型技术相结合,能快速实现模型的复制,改变了传统的产品开发设计和制造模式。快速成型要求曲面必须保证一定的制作精度和光顺性,本文基于Imageware软件,结合具体的案例,就曲面构建方法和曲面的拼接质量影响因素进行了探讨,提出了较为完整的曲面逆向构建及快速成型的技术途径。     

基于离散点云直接映射STL文件的建模技术

随着计算机技术的发展,反求工程技术和快速原型技术的结合日趋紧密,纯复制的反求工程已不再适应市场发展的需要,在产品的设计和制造阶段都需要具备创新环节的反求工程技术的支持。提出综合优化的方法：对扫描后获取的离散扫描点进行平面的三角剖分及环域间的三角剖分,生成STL文件格式,并结合环域划分风格的特点,使用最小权和最小内角最大化相融合的方法,实现二维优化：当二维坐标释放到空间后会破坏三角形形状,影响模型的质量,用增加点的方法,得到三维优化后的原产品模型的STL文件格式。在布尔运算的基础上,通过对反求模型的三角网格进行任意叠加和任意截取,产生新产品的STL文件格式;对新产品进行总体形状控制、过渡圆角处理等空间优化工作,最终实现新产品创新,缩短了产品的开发周期,降低了开发成本。     

基于STL模型的轮廓线自适应分层方法研究

目前,大多数快速成型系统在表达CAD模型时仍采用STL模型。由于快速成型自身的特点,对STL模型进行分层处理是其必由之路。在分析了传统的STL模型分层方法的基础上,提出了一种基于STL模型的轮廓外形线自适应分层的方法,然后通过实例对该自适应分层方法进行了验证,证明了该方法的可行性和正确性。     

基于逆向工程的产品快速制造的研究

以吸尘器为例,详细阐述了逆向工程技术和快速成型技术在产品设计中的应用和实现。采用三坐标测量机测得吸尘器表面若干空间点数据,利用U G N X 6.0对其点云数据进行处理并完成三维C A D模型的重建,最后基于3D P技术实现对吸尘器原型的快速成型制造,从而为后续对新产品进行快速评价、结构优化验证和性能测试等方面打下坚实的基础。结果表明,逆向工程与快速成型技术相结合,为新产品尤其是复杂型面产品的设计与制造提供了更为广阔的平台,并且缩短产品开发周期、降低试制成本、避免产品研发失败的风险,可以极大地提高企业的竞争力和经济效益。     

基于"RPM"的快速反求工程

反求工程是一种应用非常广泛的新兴技术,在快速成形制造中具有重要作用。介绍了基于快速原型制造的快速反求工程系统的原理、测量方法以及数据处理方法,并指出了关键的问题和发展趋势。     

SL快速成型中支撑自动生成技术研究

针对 SL快速成型技术加工时需要对零件加支撑的要求 ,通过对 CAD模型和 STL模型文件特点的分析 ,采用直接从 STL 模型文件提取信息找到 CAD模型的待加支撑面、线、点 ,并按待加支撑面、线、点的特征给其加二维支撑 ,再确定支撑空间高度的方案 ,实现了支撑自动生成。应用表明 :该技术节省了 SL加工时的数据预处理时间 ,避免了利用人工加支撑时的人为错误 ,提高了快速成型的效率     

Rapid prototyping fabrication and finite element evaluation of the three-dimensional medical pelvic model

This paper presents a non-uniform, periodic closed B-spline approximation algorithm for the fabrication of a medical pelvic model, based on rapid prototyping, and also gives the finite element evaluation of the pelvic model. Rapid prototyping (RP), when used in fabricating medical prosthesis, has a strict requirement for closeness and impermeability of STL files. Incorrect data structure in STL files will cause the subsequent slicing process not to proceed. The non-uniform periodic closed B-spline curve approximation method was applied to processing CT data. The precision and size of STL files was improved to optimize the RP model of the pelvis. Finally, the model of the pelvis was evaluated with the finite element method. Results suggest that a high similarity has been achieved in terms of shape, size and biomechanical properties of the pelvic model and the normal one, which validates our argument that rapid prototyping with non-uniform, periodic closed B-spline algorithm is suitable for the fabrication of a pelvic model, which will prove to be significant in the design of pelvic prostheses .     

基于Matlab三维数据点三角剖分方法研究

逆向工程中点云数据点三角划分处理,在散乱数据插值曲面构造、快速原型制造以及有限元分析等方面有着重要的应用.根据Delaunay三角划分理论及Lawson优化准则,借助于Matlab中用于点云处理模块快速实现了空间散乱数据点的直接三角划分,给出了数据点三角划分程序代码,并以某小客车车身外表面点云数据处理过程加以验证,给出其外形数据点Delaunay三角划分以及凸壳包络图,由此可以早期发现逆向设计过程中可能存在的问题,从而减少后期修改次数,极大缩短新产品的开发周期,提高了设计精度.     

Generation of an STL File from 3D Measurement Data with User-Controlled Data Reduction

Reverse engineering is a methodology for constructing com-puter- aided design (CAD) models of physical parts by digitising an existing part, creating a computer model and then using it to manufacture the component. When a digitised part is to be manufactured by means of rapid prototyping machines such as stereolithography apparatus (SLA) and selective laser sintering equipment (SLS), etc., it is not necessary to construct the CAD model of a digitised part. This can be achieved by the proposed novel method which can construct an STL file (the de facto file format for rapid prototyping machines) directly from digitised part data. Furthermore, the STL file can be constructed with a significant data reduction at the users’ discretion.     

A novel arc-spraying robot for rapid tooling

In order to reduce the process uncertainty and the labor intensity in manual metal arc spraying for rapid tooling, this paper presents a robot wrist design and a robot motion control method based on the cross-sectional contours and related surface normal vectors extracted from STL model, a de facto standard for representing a 3D part geometry in rapid prototyping (RP) industry. A computer controlled five-axis robot for the rapid tooling was built by using the wrist, which drives the spraying gun. The wrist comprises a linkage that can maintain the working position of the gun while changing its spraying orientation freely. Such a design ensures that adjusting the gun along the normal of the master surface to satisfy the process requirement will not result in any position change of the spraying point. A kinematic analysis on the wrist indicates this kinematic decoupling between the positioning mechanism and the orientating mechanism. The working trajectory of the gun is generated off-line by slicing the STL model of the master pattern. To bypass the need for any teaching or NC programming, the arc-spraying robot can carry out the tooling process automatically and efficiently fully based on the sliced data of the master pattern. In addition, a case study on the production of automobile body panel dies using this robotic tooling system is introduced.