集成产品模型

产品模型作为对产品生命周期中产品信息描述的一种手段，已经成为实现制造自动化的关键技术。本文介绍产品模型的概念及其发展过程，从零件信息描述裙带性和设计过程的逻辑完整性发出，提出了一种基于关系型ＣＡＤ和产品数据管理（ＰＤＭ）系统的集成产品模型，并讨论了该产品模型的特点及基本原理。     

箱体零件CAD／CAPP／CAM集成系统的研究与实践

在ＣＩＭＳ环境下，针对箱体零件ＣＡＤ、ＣＡＰＰ、ＣＡＭ信息集成的功能需求，在基于特征的箱体零件信息模型、工艺计划模型与服务于工艺设计的制造环境模型的支持下，开发出了特征造型，工艺设计及加工过程仿真与ＮＣ编程等子系统，从而完成了一个集成化的箱体零件ＣＡＤ／ＣＡＰＰ／ＣＡＭ系统。     

基于特征设计和参数设计的零件模型

为提高ＣＡＤ／ＣＡＭ系统的描述能力和效率，本文提出一种基于特征设计和参数设计的零件模模型。该模型采用了一系列新的表示方法，包括辅助点线面表示，工作坐标系表示、截面轮廓和轨迹表示、和零件模表示。辅助线面用于定位特征。     

CAD／CAPP集成系统信息建模技术研究

通过对特征技术的分析研究，基于特征技术的建模思想，设计了一个完整的产品数据信息模型，提出了一种零件ＣＡＤ．ＣＡＰＰ集成系统数据信息模型，通过网络，实现了ＣＡＤ／ＣＡＰＰ的信息交换与集成。     

面向并行工程的产品CAD系统的信息管理

面向并行工程的产品ＣＡＤ系统所涉及的信息量大面广，对该信息的管理是实现ＣＥ环境下ＣＡＤ／ＣＡＰＰ／ＭＲＰⅡ集成的关键。作者对产品ＣＡＤ系统中所涉及到的信息进行了分析、研究，为系统开发中建立共享数据库打下了基础。     

空间钣金弯曲件的形状特征建模

形状信息是产品信息的核心。本文分析了复杂弯曲件的形状特点，采用特征的方法，用特征树来表示复杂弯曲件的结构，建立了复杂弯曲件的形状特征模型，并成功地将它应用于高精度级建模ＣＡＤ／ＣＡＭ系统的开发。     

实用化的CAD／CAPP／CAM集成系统

本文介绍了一个实用化的ＣＡＤ／ＣＡＰＰ／ＣＡＭ集成系统。该系统是由机械产品设计人员、工艺人员和数控机床ＮＣ程编人员共同努力，在商品ＣＡＤ、ＣＡＭ软件Ｐｏｒ／ＥＮＧＩＮＥＥＲ平台上开发的。系统由三个子系统组成：零件信息识别子系统、ＣＡＰＰ子系统和自动ＣＡＭ子系统。零件信息识别子系统从三维零件中提取零件信息，ＣＡＰＰ子系统分析零件信息，自动生成零件加工工序加和工步，从刀具数据库中查询刀具及切削用量，并     

CAD/CAM 系统中曲面模型真实感显示方法的研究与实现

本文介绍了由南京航空航天大学ＣＡＤ／ＣＡＭ工程研究中心开发的集成化超人ＣＡＤ／ＣＡＭ／ＣＮＣ系统中对产品模型进行着色的方法，同时介绍了该系统所运用的防变形的新方法。运用这种方法实现产品模型的真实感显示，速度已达到实用的要求。效果良好。     

基于参数化特征建模的信息集成系统—FVCAD

本系统在自行开发的二维参数化绘图系统ＶＣＡＤ基础上，建立一个三维特征征库，在零件的二维设计过程中采取以零件的方位面为单元建立机械零件的特征模型，实现ＣＡＤ／ＣＡＰＰ／ＣＡＭ的信息集成。     

面向客户化设计的包装容器CAD系统

提出了面向客户化设计的ＣＡＤ系统开发思想,给出了面向客户化设计的包装容器ＣＡＤ系统的模型框架给出了功能知识表示方法和基于功能约束的形状设计方法。     

网络化设计和制造信息共享中的STEP和XML技术

在网络化设计和制造中 ,各个协同工作用户所使用的系统类型具有不确定性 ,随之而产生的一个重要问题 ,就是如何通过互联网来实现异质系统之间的信息集成问题 .本文提出了一种新的理论方法 ,该方法建立在STEP和XML基础上 ,可以使网络化制造中的CAD系统之间、CAM系统之间、以及CAD和CAM系统之间通过互联网实现信息共用 .文章介绍了相关的STEP标准和XML概念 ,以及相对应的EXPRESS和DTD标准 .同时详细介绍如何将STEP和XML作为中性格式模型集成在一起的思路 ,最后 ,提供了一个建立在STEP和XML基础之上的系统框架     

参数化CAD中参数有效范围的算法研究

为了解决在参数化CAD系统中由于参数赋值不合理而导致的几何实体重建失败的问题,提出了确定一类二维参数化CAD模型中参数有效范围的代数算法。该算法可以实时求解所有简单多边形中距离约束参数的有效取值范围,并利用几何变换简化求解规模,提高求解效率。研究结果表明,该算法提供的有效取值范围内的任一赋值,均可保证重建后几何实体的拓扑形状不发生改变,在一定程度上提高了参数化CAD软件的设计效率和人机交互的智能化水平。同时对算法复杂度进行了分析,该算法的复杂度为O(n~2)。     

Voxel-based shape analysis and search of mechanical CAD-models

3D model search techniques play an important part in facilitating design reuse. This paper discusses 3D model searching issues in the application domain of mechanical CAD. For mechanical CAD models, both geometrical information and topological information are important for similarity assessment. We proposed two shape signatures to describe the geometry and the topology of a mechanical CAD model respectively. The two shape signatures are extracted from voxelized models. Experimental results suggest that the proposed method can help engineers effectively search out wanted models in several ways.     

Point-based approach to enhance the quality of geometric data for CAE applications

Commercial CAD surface modelling software is based almost exclusively on Bézier, B-spline and NURBS representations. These methods offer simple interactive shape modification and computationally efficient interrogations, but have some serious practical limitations. The root cause of all these problems is that the parametric polynomial methods are not geometry-based, and the trouble is compounded by the master geometry philosophy which treats the CAD model as if it were absolutely correct. An alternative purely geometric approach to surface modelling has been established, where the surface shape is characterised by a grid of points lying on the surface, but it is recognised that this approach would require major changes in existing CAE systems. This application paper explains the rationale to develop algorithms, which would plug into existing CAE software systems, so that the user could benefit from the point-based construction without disturbing the established mode of operation. The new point-based approach has achieved significant success in ensuring that form tools produce panels within a specified tolerance.     

A CAD-based tool for development of large layouts

This paper focuses on the development of a CAD-based tool for the design of complex systems layout, where the primary objective is to compress time to market. We describe the concept for a library which contains necessary information for the conceptual stage of the design process based on the features technology. The stored information has both geometric and non-geometric characteristics. Geometric information is the core of the CAD-based tool. It is in the form of a geometry library which contains systematically abstracted 3-D CAD models. We introduce guidelines for geometric abstraction so that large layouts can be constructed and analysed in 3-D CAD systems. Besides a simplified version of the virtual model of a product, non-geometric information such as functionality, mode of action, costs, material properties, etc., are provided. The method described has been applied for the design of complex train equipment. The results reveal that the lead time required to develop an equipment layout is reduced to about 70 compared with early designs.     

Structural shape and topology optimization of cast parts using level set method

This paper presents a level set‐based shape and topology optimization method for conceptual design of cast parts. In order to be successfully manufactured by the casting process, the geometry of cast parts should satisfy certain moldability conditions, which poses additional constraints in the shape and topology optimization of cast parts. Instead of using the originally point‐wise constraint statement, we propose a casting constraint in the form of domain integration over a narrowband near the material boundaries. This constraint is expressed in terms of the gradient of the level set function defining the structural shape and topology. Its explicit and analytical form facilitates the sensitivity analysis and numerical implementation. As compared with the standard implementation of the level set method based on the steepest descent algorithm, the proposed method uses velocity field design variables and combines the level set method with the gradient‐based mathematical programming algorithm on the basis of the derived sensitivity scheme of the objective function and the constraints. This approach is able to simultaneously account for the casting constraint and the conventional material volume constraint in a convenient way. In this method, the optimization process can be started from an arbitrary initial design, without the need for an initial design satisfying the cast constraint. Numerical examples in both 2D and 3D design domain are given to demonstrate the validity and effectiveness of the proposed method. Copyright © 2017 John Wiley & Sons, Ltd.     

在Pro/E中自动生成零件拆卸优先约束矩阵

拆卸优先约束矩阵为建立产品的拆卸层次信息图模型提供了基础信息,保证了拆卸序列规划结果的正确性和有效性.在Pro/E中用C语言完成了零件拆卸优先约束矩阵自动生成的二次开发,包括模型调入和预处理、简单拆卸路径生成和包容盒逐级分解的干涉检验等3个模块.解决了自动判别节点可拆卸性的关键问题,为机电产品基于拆卸层次信息图建模的自动化提供了有力的支持.     

STEP-based approach for direct slicing of CAD models for layered manufacturing

Direct slicing can generate precise slice contours from original CAD models and obviates the error-detection and repairing process of STL files. At present, most direct slicing approaches are restricted to some CSG solids or particular CAD packages. In this paper, an approach for direct slicing of CAD models based on STEP for layered manufacturing is presented. The original CAD model is first transferred from CAD systems to the slicing system by neutral STEP files. Using OpenGL graphics libraries, the solid model is then displayed, and the user is prompted to specify the layer thickness. Finally, the CAD model is sliced directly, and the sliced model is exported by SSL (Stratasys Layer interface files) file format which can be sent to many kinds of layered manufacturing systems for direct fabrication. The approach of STEP-based direct slicing is more flexible and does not rely on any specific CAD system; in addition, the STEP files are much smaller than the STL files. Implementation details and results are also presented.