An IGES post-processor for interfacing CAD and CAPP of 2 1/2D prismatic parts

An IGES post-processor is presented, written in FORTRAN-77, to extract from an IGES file all information that an automatic process planning program needs, derive new information when necessary and formalise it as PROLOG facts. The processor deals with wire frame models and drawings. Its various modules are described and considerations about its design are discussed, associated with the IGES specification philosophy and pre-processor implementations. Analogous approaches from other processor designs are reviewed.     

Knowledge-based automatic allocation of cad drawing annotation to wireframe iges models of 2 1/2-D prismatic parts

A knowledge-based Prolog program is presented that interprets the annotation information of a CAD drawing in terms of geometry primitives derived from the wireframe model used to create the drawing. The knowledge base consists of rules for recognising drawing symbols, parsing annotation text, identifying the connecting elements between text and geometry, suggesting geometry primitives to be sought for different annotation entities, and defining geometric connectivity relations. This enables the knowledge base to be incrementally developed to cater for more cases. So far, size tolerances, surface finish and some drawing notes are dealt with by the system. All the information needed as input is obtained from the component's IGES file.     

CADEXCAP: Integration of 2D CAD models of turned components with CAPP

EXCAP is a knowledge-based process-planning system for turned components. This paper describes a software package called CADEXCAP, which has been developed to integrate EXCAP and CAD systems via IGES. CADEXCAP deciphers a full 2 D model of a turned component developed on a CAD system and then, via IGES, fully automatically generates a product model in the EXCAP model format. It is clever enough to extract not only the geometrical information but also the other required information, such as geometrical and dimensional tolerances, surface finish and manufacturing instructions.     

Automatic simplification of solid models for engineering analysis independent of modeling sequences

Although solid models can represent complex and detailed geometry of parts, it is often necessary to simplify solid models by removing the detailed geometry in some applications such as finite element analysis and similarity assessment of CAD models. There are no standards for judging the goodness of a simplification method, but one essential criterion would be that it should generate a consistent and acceptable simplification for the same solid model, regardless of how the solid model has been created. Since a design-feature-based approach is tightly dependent on modeling sequences and designer’s modeling preferences, it sometimes produces inconsistent and unacceptable simplifications. In this paper, a new method is proposed to simplify solid models of machined parts. Independently of user-specified design features, this method directly recognizes and generates subtractive features from the final model of the part, and then simplifies the solid model by removing the detailed geometry by using these subtractive features. This paper was recommended for publication in revised form by Associate Editor Jeong-Sam Han Yoonhwan Woo is an assistant professor of Mechanical Systems Engineering at Hansung University in Korea. He received his Ph.D. in Mechanical Engineering from Colorado State University in 1999, the M.S. in Mechanical and Aerospace engineering from Illinois Institute of Technology in 1995, and the B.S. in Precision Mechanical Engineering from Hanyang University, Korea, in 1993. He also has been a software engineer of ACIS development team in Spatial Corporation, USA. His research interests include geometric and solid modeling and computer aided process planning.     

Guidelines for building 2D CAD models of turned components in CAD-CAPP integration

EXCAP is a knowledge-based process-planning system for rotational components. CADEXCAP is software which has been developed to integrate EXCAP with CAD systems via IGES (Initial Graphics Exchange Specification). CADEXCAP deciphers a full 2D model of a turned component developed on a CAD system and then via IGES it fully automatically generates a product model in a format suitable for EXCAP. This paper describes the guidelines which have to be followed at the CAD modelling stage of the components which are to be used by CADEXCAP. Following these guidelines will guarantee the automatic extraction of complete product models. This not only includes the geometry but also includes nongeometric information such as toleranced dimensions, geometrical tolerances, manufacturing instructions and surface finish.     

基于顶点的冲裁零件排样系统

分析了冲裁件排样优化存在的问题 ,统一了材料利用率计算公式 ,提出基于顶点的一步平移优化算法。该算法可以有效减少计算量 ,较好地处理冲裁件图形圆弧、曲线线性化问题 ,有利于建立一个完整的冲裁件 CAD/CAM系统     

反求工程技术在新产品开发中的应用

介绍了反求工程的基本概念和体系结构,着重阐述了反求工程中的两种基本设计方法及其具体实施过程,分析了其实施过程中所运用的CAD/CAE/CAM等计算机辅助技术,以及如何根据测量中所得到的数字化数据构建出实体模型,从而开发出新产品。     

基于逆向工程的发动机叶片实体建模关键技术研究

发动机叶片是航空发动的关键零件，计算机技术的发展和功能强大的三维造型软件的出现为超薄扭曲叶片的三维实体建模带来了极大的便利。本文在逆向工程设计思想的指导下，就航空发动机叶片特有的结构和技术要求，着重讨论了叶片实体建模中型面测量数据预处理、叶身型线与进排气边过渡圆弧切点的校正和叶身B样条自由曲面拟和等关键技术问题，并对叶片型面的光顺度和平滑度进行了校验，从而获得符合设计要求的叶片实体模型。     

Assessment of space division strategies for generation of adequate computational models for solid foams

The present study is concerned with a competitive assessment of different strategies for the division of space in the generation of computational models for the microstructure of solid foams for a numerical analysis of their properties. The study includes the standard (Γ‐) Voronoi procedure, the δ-Voronoi procedure, a Voronoi procedure in Laguerre geometry as well as a simple foam evolution strategy. In addition to the basic versions of the individual strategies, smoothing and optimization approaches are used for a further improvement of the generated computational models. The quality of the models is assessed in terms of two quantitative criteria where the first criterion is the Kelvin parameter whereas the second criterion is based on the error in the statistical cell size distribution compared to experimental observations reported in the literature. All strategies are applied to the simplified case of two-dimensional model foams. Nevertheless, the results can be generalized to the three-dimensional case in a straight forward manner.     

Evaluation of 1-D and 2-D models for discharge prediction in straight compound channels with smooth and rough floodplain

Accurate estimation of discharge capacity of flooding rivers is extremely important in flood control projects. Floodplains are often covered with vegetation which generally increases the flow resistance, and affects the conveyance capacity. Several numerical methods have been proposed by researchers for predicting the stage-discharge relationship in compound channels. The hydraulic behavior of compound channel flow with vegetated floodplains is very complex. Hence, the accuracy of numerical discharge prediction methods must be investigated in compound channels with vegetated floodplain. In this paper, experimental results are presented for flow capacity of an asymmetric compound channel with vegetated and non-vegetated floodplain. An attempt has been made to compute the discharge with different 1-D and 2-D methods, including Single Channel Method (SCM), Divided Channel Methods (DCMs), Coherence Method (COHM) and Shiono and Knight Method (SKM). The results are then compared with experimental data. The results show that the SKM model is more accurate in discharge prediction than other models studied in the present study. Also, the DCM-ID model is found to be less accurate in discharge prediction in compound channels with smooth or rough floodplain.     

Implementation of a Robot System for Sculptured Surface Cutting. Part 1. Rough Machining

Rapid prototyping plays an important role in product development. There are two ways to realise rapid rototyping: one is to develop new prototyping equipment such as stereolithography apparatus (SLA), selective laser sintering (SLS), etc., and the other is to improve existing CNC techniques. In this work, a robot system for rapid prototyping, which is an enhancement of the CNC based method, is presented. A robot arm holding a milling tool is used to machine the prototype of a solid model drawn using a commercial CAD system. In this paper, Part 1, a strategy using the robot for rough machining is discussed and then an automatic tool-path generation method using a grid height array is presented. This method can generate tool paths for rough machining with different tolerances. As a verification of the proposed algorithm, a number of prototypes have been produced, which have demonstrated the feasibility and advantages of the algorithm. In a companion paper, Part 2, an approach to represent C-space by incorporating possible variations in tooling orientations is proposed. In order to reduce error on complex surfaces resulting from undercut or overcut operations, a curvature-matching algorithm is developed. Finally, experimental work using the collision-free planning strategy and simulation for the curvature matching algorithm is carried out.     

双圆弧弧齿锥齿轮的实体建模方法及加工过程模拟

以双圆弧弧齿锥齿轮的加工原理为基础，借助绘图软件AutoCAD这一工具，进行了双圆弧弧齿锥齿轮的实体建模及加工过程模拟。     

Implementation of a Robot System for Sculptured Surface Cutting. Part 2. Finish Machining

Rapid prototyping plays an important role in product development. There are two ways to realise rapid prototyping: one is to develop new prototyping equipment such as stereolithography apparatus (SLA), selective laser sintering (SLS), etc., and the other is to improve existing CNC techniques. In this work, a robot system for rapid prototyping, which is an enhancement of the CNC based method, is presented. A robot arm holding a milling tool is used to machine the prototype of a solid model drawn using a commercial CAD system. In a previous paper, Part 1, a strategy using the robot for rough machining was discussed and then an automatic tool-path generation method using a grid height array was presented. As a verification of the proposed algorithm, a number of prototypes were produced, which demonstrated the feasibility and advantages of the algorithm. In this paper, Part 2, an approach to represent C-space by incorporating possible variations in tooling orientations is proposed. In order to reduce the error on complex surfaces resulting from undercut or overcut operations, a curvature-matching algorithm is also developed. Finally, experimental work using collsion-free planning for manipulator movement and stimulation for the curvature matching algorithm is carried out.     

参数切换机械系统建模研究

参数切换机械系统内部参数可以切换，因而系统能在一个给定输入下产生多个期望输出。通过阐述数列集合上的代数运算，建立系统的数学表达式及其拓扑表示，揭示系统知身具有计算规律，讨论系统的相似变换和参数结构，为系统设计和智能应用提供数理基础。     

The friction behavior of Ni-, SiO2- and mica sodium silicate-based solid lubrication composites

The friction behavior of Ni⁻-, SiO⁻₂- and mica sodium silicate-based lubricant composites, which included BN, WS₂ and graphite as lubricants, were examined. A ring-on-disk apparatus, in which a solid lubricant composite disk was held against a rotating stainless ring, was used as the test configuration. The tests were run with a load from 62 to 250 N in temperatures from 20 to 800°C in the laboratory environment. The wear surface was characterized by scanning electron microscope and X-ray photo spectroscopy. The major findings were that both mica sodium silicate- and SiO⁻₂-based composites failed at above 500°C due to severe wear and surface damage; in contrast, Ni⁻-based composite showed a stable friction coefficient and low wear from 20 to 800°C.     

CNC programming system for complex components based on KBE within integrated environment of CAD/CAPP/CAM

To promote the research and development of modern digital and intelligent manufacturing technology and overcome shortcomings of computerized numerical control(CNC) programming for complex components, an innovative idea has been proposed to introduce knowledge based engineering (KBE) into the field of CNC programming within the integrated environment of CAD/CAPP/ CAM. This paper constructs the architecture of CNC programming based on KBE within CAD/CAPP/CAM and explores the key technology of applying KBE to CNC programming — knowledge representation, knowledge acquisition, knowledge reasoning, and generalized knowledge base system of CNC programming. The integration of the CAD/CAM system and the CAPP system of enterprises has been achieved by taking the powerful CAD/CAM system of UG NX as a platform. The prototype system of CNC programming for complex components based on KBE within CAD/CAPP/CAM has been developed by means of UG/Open,VC ++ 6.0, and SQL Sever 2000. Finally, a frame example, one of the complex components of a marine diesel, is presented, and the academic production and the intelligence of the system are verified.     

面向CSCW的CAD/CAM系统设计

协同设计是实现并行工程的关键,ＣＳＣＷ为协同设计的实现提供了有力的环境和技术支持。分析了ＣＡＤ／ＣＡＭ系统实现协同设计的方法和步骤,提出了一个ＣＳＣＷ环境下的基于代理的ＣＡＤ／ＣＡＭ系统模型,并对模型中协同设计环境的构造、各代理结构的设计以及分布协同设计环境下产品模型的处理作了分析。     

超声波流量计高分辨率A/D转换电路设计与实现

针对高精度时差法超声波流量计的时间差信号采集问题,采用一款双通道12位低功耗单片CMOS模拟数字转换器ADC12DL040芯片设计并实现了超声波流量计ns级时间差的高分辨率数据采集,给出了A/D芯片外围引脚电路设计,软件流程图和关键代码,实现了400 kHz输入频率,8 MHz采样频率的超声波时间差高分辨率实时采样.     

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.     

Experimental study on integration of laser-based additive/subtractive processes for meso/micro solid freeform fabrication

Solid freeform fabrication has attracted considerable attention lately because of its ability to build a 3D structure with a complex and arbitrary shape. This work presents initial studies to adapt this technology for the fabrication of meso-/micro-3D structures. A pulsed Nd:YAG laser was used for laser microdeposition (additive) and micromachining (subtractive) processes. An ultrasonic-based micropowder feeding system was developed to generate precise patterns of micropowders on a substrate without any pre-processing. Laser microdeposition of copper and stainless steel micropowders was accomplished. The characterization of micromachining was performed on stainless steel and copper plates with a laser beam of wavelengths of 355 nm and 266 nm. The integration of laser microdeposition and micromachining processes improved the resolution and edge quality of the meso-/micropatterns.