Integration of CAD and a cutting tool selection system

This paper describes a novel concept for the integration of a CAD system and a knowledge based system of the selection of cutting tools and conditions for turning operations (EXCATS). This integrated system (CADEXCATS) is capable of processing CAD data and automatically generating the component representation file for EXCATS using the IGES neutral format and a feature recognition approach. The workpiece representation model is capable to describe sophisticated turned components using Prolog facts and other operational linked keywords. In addition, CAPP related features are effectively incorporated into the CADEXCATS system. A set of rules is established for the automatic determination of set-up, detection of complex geometries, recognition of grooves and other important features. Illustrative examples are presented to test and validate the developed system.     

IGES Model Comparison System: A Tool for Tsting and Validating IGES Processors

The IGES Model Comparison System (IMCOS) is the first test tool to allow an easy and automatic semantic comparison of CAD models represented in IGES format. By systematically analyzing and comparing entity data and structures of generated and exchanged IGES models, it detects loss of information and functionality resulting from model exchange via IGES processors. IMCOS was designed and implemented as a tabledriven IGES processor to allow external control of the comparison process and full coverage of the current version of IGES (Version 3.0) and future versions. This article presents the basic concepts of IMCOS. The great interest in and discussion of IMCOS have shown the importance of such a test tool. IMCOS may be used as one of several test tools within an overall IGES verification program.     

滚子链传动CAD程序设计

本文介绍滚子链传动ＣＡＤ系统的程序设计，以及链轮零件图绘制等内容。主要阐明链传动设计计算程序设计的理论根据和基本方法，链轮零件图图形处理方法，实现了链传动设计计算过程和绘制链轮零件图的一体化过程。     

Computer aided engineering of automated guided vehicle systems

Automated Guided Vehicle Systems (AGVS) are becoming more and more the main material handling devices in flexible manufacturing systems. The design of an AGVS network is a complex, iterative process. It requires a sequence of geometrical layout drawings and an analytical and computational evaluations. The ability to analyze the AGVS design directly and interactively from the layout drawing would substantially increase the productivity of the design engineer.

A Computer Aided Engineering (CAE) design tool must provide the following three capabilities. First, it must allow the easy, interactive and graphical definition of the system by providing standard drawing symbols and the required operations on those symbols. Second, it must support direct, interactive analysis of the design from within the drafting package. Third, it must provide for the necessary output to interface with off line simulation, analysis and verification programs.

The possibility of extending the prominent CAD packages CADAM and AutoCad to perform CAE of AGVS is examined. A prototype of such a CAE tool has been developed based upon the Autocad package and implemented on a microcomputer. Design and implementation issues, as well as future research areas, will be reported on.     

CAD图纸工件可视化系统

该文给出了一个能够完成CAD图纸工件可视化过程的可视化系统。分别介绍了可视化系统的四个主要功能模块：IGES文件提取和识别、三维重建、图形学模型建立和优化以及可视化模块。并给出了一个具体的实验。     

基于哈希的二维工程 CAD 图纸检索技术

针对企业在设计创新过程中大量采用已有计算机辅助设计(CAD)图纸进行设计重 用的情况,提出了一种基于哈希的二维工程 CAD 图纸检索方法。首先基于环形分割算法提取 工程 CAD 图纸中每个组件对象几何特征;基于传统 LBP 算子提出了一种局部拓扑矢量量化模 式(T-LVQP),实现对各个组件拓扑特征的提取;然后基于协方差描述符融合几何特征和拓扑特 征,通过 LBG 算法将所有组件按照几何特征分组后得到工程 CAD 图纸的特征向量表达;最后 通过迭代量化哈希算法生成图纸的哈希序列。实验结果表明,该算法检索速度快、准确度高, 对于二维工程 CAD 图纸具有较好的检索效果。     

一种实现小幅面工程图拼排打印的方法

对HPGL/2格式的工程图形文件进行了分析,针对CAD软件以及绘图机在排版打印方面的不足,设计了将多张小幅面的工程图合并为一张大幅面图形的方法,以Delphi 7.0为开发工具开发了基于HPGL/2格式的工程图拼排打印程序.     

基于DAG 表示与产生式的IGES 装配体数据交换算法

初始图形交换规范（IGES）是目前应用最为广泛的中性文件格式标准之 一,但是相关的研究主要集中在单零件的格式转换上面,对设计中经常用到的装配体的IGES 格式研究较少。该文总结了常用CAD 软件中装配体导出的IGES 文件存储格式,提出并实 现了一种基于图表示与产生式规则的IGES 装配体数据交换算法,将IGES 格式的解析过程 标准化,使其具有通用性和可扩展性,并且正确性可以进行形式化验证。应用该方法,该文 具体实现了多文件格式的装配体IGES 前置和后置处理器。在几何造型系统TiGems7.0 中进 行的实验结果表明该算法具有较快的速度,也具有较好的鲁棒性。     

Process Planning System in the CIM Environment

This paper describes an approach to the integration of Process Planning with Computer Aided Design and Computer Aided Manufacturing functions. The link is established through IGES which is used to transfer the geometric data from the CAD system to the process planning system. The process planning system can subsequently use this data in generating a detailed process plan as well as an NC part program for the manufacture of the part and can therefore be used as the basis of true integration between CAD and CAM.     

Importing mesh entities through IGES/PDES

IGES/PDES is an internationally accepted standard for transferring solid model information between different CAD/CAM software. Most of the information, like geometric entities, mesh entities and drafting entities, for a model generated in a particular software may be imported into another software through the IGES protocol, although either software may have its own internal database structure, radically different from each other. The goal of this article is to outline the basic concepts involved in extracting relevant information from an IGES file produced by a CAD/CAM software. In order to elucidate the process involved, only the mesh entities (nodes and elements) are brought in and a simple F77 code is attached, which could easily be extended to develop a general purpose IGES translator for pre-processing in a Finite Element/Boundary Element based analysis environment.     

Frontal geometry from sketches of engineering objects: is line labelling necessary?

A tool which can quickly interpret line drawings (with hidden lines removed) of engineering objects as boundary representation CAD models would be of significant benefit in the process of engineering design. Inflation of the drawing to produce a frontal geometry, a geometric realisation of that part of the object visible in the drawing, is an important stage of this process.Previous methods of producing frontal geometries have relied on the technique of line labelling (labelling edges as convex, concave or occluding). Although restricted subsets of the line-labelling problem have known solutions, reliable methods have not been found for the general line-labelling problem, and traditional methods, when adapted to drawings with non-trihedral junctions, are unacceptably slow.Many other papers assume that line labelling is an essential step. Here, we show this is not necessarily true, and that comparable results can be obtained by a novel alternative approach. Firstly, we consider what outputs from line labelling are essential to the production of frontal geometry. Secondly, we investigate by what other means these outputs can be produced.Our work indicates that the only essential output from line labelling for frontal geometry is the determination of which T-junctions in a drawing are occluding and which are non-occluding. This information is required for inflation, and also for detection of symmetry and for constructing hidden topology.Thus, we propose and analyse a new method which, in the absence of line labels, simultaneously inflates a drawing to produce the frontal geometry and attempts to determine whether each T-junction is occluding or not. For drawings of objects with holes or pockets, and for cases where line labelling is particularly unreliable, our new method can provide a better alternative.     

Some algorithms to correct a geometry in order to create a finite element mesh

One of the major difficulties in meshing 3D complex geometries is to deal with non-proper geometrical definitions coming from CAD systems. Typically, CAD systems do not take care of the proper definition of the geometries for the analysis purposes. In addition, the use of standard CAD files (IGES, VDA, …) for the transfer of geometries between different systems introduce some additional difficulties.In this work, a collection of algorithms to repair and/or to improve the geometry definitions are provided. The aim of these algorithms is to make as easy as possible the generation of a mesh over complex geometries given some minimum requirements of quality and correctness. The geometrical model will be considered as composed of a set of NURBS lines and trimmed surfaces.Some examples of application of the algorithms and of the meshes generated from the corrected geometry are also presented in this work.     

CAD Standard parts file — A DIN project in the standards committee on tabular layouts for article characteristics

The project was started in December 84, to define the necessary data records, to handle standard parts on CAD systems and work stations.

Basis of the data records were the article characteristics, documented in the German Standard DIN 4000. The aim is to add information on the logical structure of the standard parts from the tables in the “Product Standards”.

During the first year of work it was noted that the user of the data will have a more efficient implementation, if corresponding standardized software is available to produce the selected graphic- and model-representation in the CAD systems. This is to be realized in close cooperation with the German NAM 96.4 (Standardization Committee for Manufacturing of Machines) and the corresponding ISO/TC 184 SC 4 (Industrial Automation, External Representation of Product Definition Data) as well as vendors and users of CAD systems.

The software will be realized on a FORTRAN basis. The relevant FORTRAN-Extension has been documented in the Prestandard DIN V 66304.

The results of the project offered by DIN shall be:

1. - standardized data records and software for the mostly used standard parts

2. - tested and actualized files and subroutine-libraries

3. - DIN certificates in a neutral form, e.g. independent from features of specific CAD systems.

     

图纸自动化生成系统的设计与实现

为了解决CAD绘图工作量日益增大、修改图纸工作繁琐并且容易出错的问题,建立一个能根据产品参数自动生成图纸的系统是非常必要的。通过对CAD图纸进行扩展处理,把图纸中需要变动的部分定义为变元,并把变元与数据库表中的字段建立关联,然后定义各变元之间的约束关系,就可以建立产品图纸的母图,进而构造出母图数据库。这样只要确定了图纸的“实参”——变元值,即可自动生成CAD图纸。     

PC-based autorouting: an evaluation

Autorouting is the most time-consuming aspect of PCB design. A designer will, on average, spend more than half the layout time either using the autorouter or manually finishing those parts of the layout left unrouted; and a typical CAD user could spend up to 1000 hours per year routing.

The paper looks in depth at PC-based autorouters and argues that the most recent developments now put the capabilities offered by these packages on a par with 32-bit CAD system autorouters.

The article aims to assist CAD users with very little time to evaluate autorouters quickly and so find one that will work well with their layout rules and design technology.     

室内设计计算机效果图制作流程优化研究

本文针对室内设计效果图制作所使用教材中制作流程不够合理、导致出图速度慢等问题,提出了优化效果图 制作流程的解决办法,包括导入CAD图纸、改变材质和灯光的设定顺序、针对灯光和材质分别测试、使用光子图加快出图速 度、将正式出图的TGA格式改为质量更高的TIF 文件、用转换插件生成材质通道图等,有效提高室内设计效果图制作的速度 和质量,使学生掌握实用性更高的制作方法,提高了教学的效果。     

Collocation and galerkin finite element methods for viscoelastic fluid flow—I. : Description of method and problems with fixed geometry

Collocation and Galerkin finite element methods are developed for viscoelastic fluid flow in a fixed geometry. The collocation methods use Hermite cubic polynomials with a global coordinate transformation to permit irregular geometry. The Galerkin method uses isoparametric elements (transformed element by element) with bilinear polynomials for pressure and quadratic polynomials for velocity. Both methods are applied to two-dimensional flow in planar geometry and the Galerkin method is applied to axisymmetric cylindrical geometries as well. The fluid model is a nonlinear Maxwell model but is limited to small elastic components.

The two methods are applied to several test problems. Entry-length problems test the ability to model pressure singularities are velocity discontinuities. Stick-slip problems test the ability to model pressure singularities and stress discontinuities. Both test problems have analytic or accurate numerical solutions for Newtonian fluids so that the accuracy of the two methods is compared.     

工程图纸向CAD系统自动输入处理

初步实现了一个工程图纸的自动输入与识别系统。该系统把工程图纸的扫描数字化图象进行矢量化,转换成CAD系统可以接受的文件格式。研究了扫描图象的预处理和矢量化方法:预处理包括图纸扫描输入、图象二值化、图象平滑与去噪、线条细化和曲线跟踪;矢量化采用直线拟合方法。提出了一种改进Hilditch细化算法并给出了程序实现方法,有效地减小了图像骨架偏移和毛刺对细化结果的影响。该文开发的系统可以识别含有直线、圆和圆弧等简单图形的工程图纸。