CAD数据转换格式的对比

随着CAD技术应用的日趋广泛,数据交换的需求也会越来越多,并且以CAD模型的方式来传递数据将会越来越普遍。这里就汽车行业CAD系统之间数据交换的问题,对现在常用两种格式(IGES和STEP)比较,分析了STEP格式代替IGES格式成为行业标准的可能性。     

异构CAD系统间的几何约束在线交换

为保证不同CAD系统之间在线交换时几何约束的一致性,提出了一种异构CAD系统间的几何约束在线交换方法。通过分析主流CAD系统的几何约束差异性,给出了几何约束的中性命令表示;接着给出了几何约束的系统命令与中性命令的双向转化算法,并重点介绍其中的差异性解决方法;最后通过实验进行验证。实验验证结果表明,提出的几何约束在线交换方法能够有效地支持几何约束在异构CAD系统间的实时创建、修改和删除操作。     

异类CAD系统间基于网络的数据准实时交换技术

为了使异类商用计算机辅助设计系统经网络实现简单、低成本和准实时交换设计数据,将几何特征建模方法归纳为块、面和过渡三类特征,随后提出创建每类特征的层次化描述方法,使其不仅易于用可扩展标记语言语言表达,而且具有可选择任意数据段传输的优点,并重点实现了创建体特征的可扩展标记语言表达.为了实现数据准实时交换,采用文档对象模型规范编程实现了可扩展标记语言数据的网上传输,并基于Web Service架构建立了Web服务器,数据的需求者通过发送请求可随时下载已上载到服务器中的数据.为了使被交换的数据在不同客户端保持一致,根据为特征定义的标识ID,分别在客户端和服务器端建立了一张ID与特征创建信息的对应表,任一时刻参与的设计者都能方便地使数据保持同步.     

传动系统CAD平台中数据处理方法研究

在传动系统CAD平台的设计中，涉及大量的设计数据和标准规范，从设计计算到图形输出都是以数据处理为中心来组织的。这里结合机械传动CAD系统设计过程的具体要求及其数据特点，采用了程序化和数据文件的方式来管理数据。重点论述了交互式输入、程序化处理和一维数表、二维数表的数据文件管理方法，并基于AutoLISP语言实现了整个CAD系统的数据管理。达到了数据利用率高、程序结构性好、模块性强的目的,减少了开发过程的复杂性。     

CAD与CAPP集成中数据文件实时修改的一种新方法

基于特征拼装CAD／CAPP集成系统，提出了一种实时修改CAD数据文件的新方法。文中采用实时修改技术，通过数据文件和数据字典文件，将数据读入二维数组中。在修改零件信息时，可直接实时修改数据表单中的零件信息，其修改简捷、方便。该方法巳成功地运用于港机轴类零件集成之中。其基本设计思想对正在从事研究基于特征的CAD／CAPP集成系统有一定的参考价值。     

ADAMS与UG、SolidWorks的数据交换实践

利用UG、SolidW orks等三维CAD软件强大的建模功能,将建好的模型导入ADAMS,以弥补ADAMS建模能力弱的不足;讨论了ADAMS与UG、SolidW orks等CAD软件的数据交换过程。     

异构CAD平台网络零件库系统的研究与实现

为满足不同CAD用户间三维零件资源共享和重用的需求,围绕多CAD平台和网络化,建立了异构CAD平台网络零件库系统体系结构,提出了零件通用三维浏览模型、零件调用与参数化驱动和零件库建库工具的实现方法和过程.并综合应用CAD软件的二次开发接口、AJAX异步通信、Web3D等先进技术,在.NET框架下开发出了针对机电典型行业中标准化、系列化零件三维图形的网络零件库系统,能实现零件三维模型在线浏览和参数化驱动,并能实现对网络零件库数据的有效管理与扩充.     

Extraction of machining features for CAD/CAM integration

Feature-based CAD/CAM integration is a technology used to realise automatic transmission and conversion of component information among CAD, CAPP and CAM applications. A feature is the medium of information transmission in the integration. Since a process planning downstream application has a different viewpoint from the component designer, feature conversion or feature extraction methodology is used to create a machining feature model based on the design feature model. One of the major difficulties in generating machining features is the preservation of feature integrity because of feature interactivity. The most current research, therefore, focuses on the planar-type form feature conversion. This paper discusses the problem of feature interactivity and proposes a feature-based approach to generating hole-series machining features from a design feature model. Hole-series features are important machining features for gearbox components used in machine tools. These kinds of features cannot be obtained directly from a design feature database. A constraint-based method is developed in this paper to define a hole-series feature model based on the geometric and topological information extracted from the design database. In addition, a STEP file is generated to interface the converted machining feature model with the downstream CAPP application. The implemented feature conversion system is verified by considering its application to some component examples and the developed prototype CAPP system. This revised version was published online in October 2004 with a correction to the issue number.     

基于STEP的曲面数据交换

讨论基于STEP的两CAx软件曲面数据交换的接口设计 ,介绍STEP中关于曲面部分的定义和实现 ,给出自行设计的曲面数据转换接口原理。     

基于特征设计的轴类零件CAD/CAPP集成系统研究

以轴类零件为例，从特征定义分类、零件的设计特征与制造特征、图形数据库的建立以及特征描述与建模过程等方面，系统研究了基于特征设计的零件CAD／CAPP集成系统，同时分析了CAPP系统对CAD系统的信息重组过程。     

基于SolidWorks和CAXA数据交换的支盘成形机减速齿轮设计研究

CAXA以及SolidWorks之间的数据交换设计支盘成形机减速齿轮模型,并讨论了CAXA与SolidWorks的数据交换实现过程.     

特征实例CAD/CAPP系统决策优化方法研究

介绍了一种基于特征实例的箱体零件CAD/CAPP系统,系统基于特征库技术,利用CAD子系统完成箱体零件特征造型,形成描述性文件供CAPP子系统提取,实现CAD/CAPP集成.系统根据描述的特征信息与特征实例库进行匹配,以获得各特征加工链,并针对CAPP中的工艺路线决策中诸多模糊信息和模糊因素,提出了一种通用模糊综合评价法,提高了工艺路线决策结果的合理性和实用性.     

Interface between CAD and Rapid Prototyping systems. Part 2: LMI — An improved interface

The STL (STereoLithography) file format, as developed by 3D Systems, has been widely used by most Rapid Prototyping (RP) systems and is supported by all major computer-aided design (CAD) systems. However, it is necessary to improve the STL format to meet the development needs of RP technologies. In Part 1, several existing and proposed formats have been discussed. This paper, Part 2, will present an improved interface between CAD and RP systems. The new interface is a file format that supports the STL format, removes redundant information in the STL format and adds topological information to balance storage and processing cost. In addition to supporting facet boundary models, the new interface supports precise models by using the edge-based boundary representation. This paper discusses the design considerations of the new interface and data structures for both facet models and precise models. Finally, a comparison of the new interface and the STL file format will be made.     

A novel data decomposition and information translation method from CAD system to virtual assembly application

Virtual assembly (VA) is a key technology for virtual manufacturing systems. So far, CAD systems are still the main modeling tools for the VA system. There isn’t a standard data exchange criterion to transfer the data directly from CAD systems to VA applications, consequently an original data decomposition and information translation method (DDITM) was timely proposed to achieve the decomposition and translation. The information of the assembly bodies in the CAD system was divided into geometry information, topology information, and assembly information, etc., which were transferred to the VA application separately. The geometry information including the surface information was translated by the data translation interface (DTI) developed, the topology information was translated by a five-hierarchy topology structure (FHTS) constructed, and the assembly information was translated with database technology. A systematic architecture was formed with the interaction between the geometry information and the topology information, and the assembly information and the topology. Finally an experimental VA system was set up to verify the DDITM, and an assembly simulation was implemented to verify the assembly information further, which proves the translated information is precise and sufficient.     

三维CAD语义建模及其应用研究

研究语义级的三维CAD建模方法,并在三维CAD智能培训平台上进行了应用。首先介绍了基于XML的数据级建模和基于Semantic Web的语义级建模;然后探讨了面向三维CAD的静态的几何特征建模和动态的造型过程建模;最后基于语义建模在三维CAD系统环境下开发了智能培训系统,验证了本文方法的有效性。     

Profile-based feature representation method and its application in data exchange from mechanical CAD systems to ship CAD systems

The profile-based features of a mechanical Computer aided design (CAD) system commonly have complicated shapes because of the guide curve, which is of free-form type. However, while considering interoperability between heterogeneous CAD systems, this kind of free-form guide curve makes it difficult to represent the corresponding feature shape in other CAD systems; for example, ship CAD systems usually use relatively simple shape primitives to represent objects. Thus, we propose a straightforward algorithm to represent profile-based features that is based on guide curve approximation using line and arcs segments. In addition, the solid alignment and filling operations are also provided to complete the entire process of solid model reconstruction. Furthermore, we apply this technique to a data exchange from a mechanical CAD system to a ship CAD system. Lastly, we use several test cases to demonstrate the effectiveness of the proposed method.

     

基于XML的CAD系统和虚拟装配系统之间的数据转换

针对计算机辅助设计系统和虚拟装配系统之间的模型转换问题,提出了基于特征的统一的产品层次信息模型,采用XML中性文档和三角面片模型文件,通过信息分解的方法,分别将在产品建模系统中建立的产品层次信息模型中的装配信息和几何拓扑信息与三角面片信息通过数据转换接口转换到虚拟装配系统中,并在虚拟装配系统中通过映射关系进行模型重构,较好地解决了计算机辅助设计系统和虚拟装配系统之间信息共享的问题,通过实例验证了研究成果的可行性。     

基于AutoCAD的常用CAD/CAM软件数据交换研究

探讨了AutoCAD、CAXA电子图板、Pro/E和MasterCAM四种软件的特点及四种软件之间数据交换的格式,并阐述了AutoCAD与常用CAD/CAM软件实现数据交换途径。     

防扩散CAD系统的研究

针对目前商业化CAD系统的安全缺陷以及在企业实施中的存在安全问题,提出防扩散CAD系统的概念,并给出一套实现方案。该方案将CAD系统和PDM系统集成起来,结合数据加密技术和数字签名技术,以实时加密为基础构建通用的防扩散CAD系统平台,能够对企业CAD图档数据提供有效的保护,对企业信息安全管理具有重要的意义。