CATC — A Computer Aided Tolerance Control system

Computer utilization in manufacturing systems is increasing at a rapid rate. Developments thus far have been disjointed. Much work needs to be done in the area of integrating computer aided design and computer aided manufacturing (CAD/CAM). Tolerance control is an important component in the integration of CAD and CAM. Selection of design tolerances affects the build-ability of a product. The selection of manufacturing processes and sequence of processes affects process tolerance stacking. Unexamined process tolerance stacking leads to scrap and rework. A computer aided tolerance control (CATC) system is presented in this paper. This system is based on the tolerance chart technique. The CATC system is interactive and uses computer graphics for information display. The system can be used for computer aided process planning (CAPP) and for CAD/CAM integration.     

云纹图案创作和制作方法的研究

随着计算机辅助设计和制造技术,现代轻纺工艺的飞速发展,轻纺行业对云纹图案的要求越来越高,但是目前国内外轻纺CAD／CAM系统对云纹图案创作和制作方法的研究普遍不足。针对轻纺行业,特别是印花行业的特点,提出了多种云纹图案创作和制作的方法和手段。同时又提出了一种全新的挂网算法,这种挂网方法特别适合印花行业的特点。这些方案能够很好地满足目前轻纺行业的要求,已经应用在轻纺CAD／CAM系统（Top98)中,在实际生产中应用的效果也非常好。     

Integrated Computer Aided Shoe-Making System

Shoemaking is one of the areas where CAD/CAM application is rapidly increasing.Thispaper introduces an integrated computer aided shoemaking system including human foot measuring,last(wooden model)measuring,last CAD/CAM and pattern CAD/CAM.The project was supported bythe 7th national economical 5 year plan.High technologies,suh as digital image processing,patternrcognition,advanced geometrical modeling and a series of sophisticated equipments and devices are ap-plied in this integrated system.Parts of the system have become commercial products.     

The ergonomics of computer aided design within advanced manufacturing technology

Many manufacturing companies have now awakened to the significance of computer aided design (CAD), although the majority of them have only been able to purchase computerised draughting systems of which only a subset produce direct manufacturing data. Such companies are moving steadily towards the concept of computer integrated manufacture (CIM), and this demands CAD to address more than draughting. CAD architects are thus having to rethink the basic specification of such systems, although they typically suffer from an insufficient understanding of the design task and have consequently been working with inadequate specifications. It is at this fundamental level that ergonomics has much to offer, making its contribution by encouraging user-centred design. The discussion considers the relationships between CAD and: the design task; the organisation and people; creativity; and artificial intelligence. It finishes with a summary of the contribution of ergonomics.     

Neural networks for estimating the tool path length in concurrent engineering applications

This paper deals with the development of a neural computing system that can predict the cutting tool path length for milling an arbitrary pocket defined within the domain of a product design, in a computer numerically controlled (CNC) setting. Existing computer aided design and manufacturing systems (CAD/CAM) consume significant amounts of time in terms of data entry pertaining to the geometries and subsequent modifications to them. In the concurrent engineering environment, where even the designer needs information from the CAD/CAM systems, such time-consuming processes can be expensive. To alleviate this problem, a neural network system can be used to estimate machining time by predicting cost-dependent variables such as tool path length for the pocket milling operation. Pockets are characterized and classified into various groups. A randomized design is described so that the training samples that have been chosen represent the domain evenly. An appropriate network was built and trained with the sample pocket geometries. The analysis of the performance of the system in terms of tool path length prediction for new pocket geometries is presented.     

An Application of Computer Graphics and Networks to Anatomic Model and Prosthesis Manufacturing

Computer graphics has now matured in medical applications from 2D and 3D presentations for diagnosis and the planning of surgery and therapy to become the key step in making hand-held models of custom prostheses. The system described here delivers 3D shape information to create skeletal models, plan corrective surgery, and directly manufacture prostheses. Implants and anatomic models are manufactured using computed tomography (CT) image data and a system to generate Instructions for numerically controlled machines. The system combines clinical imaging, an algorithm for 3D edge detection, computer communications, and computer-aided and manufacturing (CAD/CAM). This integration of technologies brings recent advances in computer-aided design and manufacturing to the local community CT scanning clinic in a cost-effective manner. Via computer communications, several hundred remote medical imaging centers can have their CT scanners connected on-line to CAD/CAM facilities that one could not support alone. Operators of the remote CT scanners bear only the cost of computer communications equipment to being their patients this service. We use the clinical course of several patients in whom prostheses have been implanted to describe this technology.     

Learning studies in the use of computer aided design systems for discrete-parts manufacture

Two-dimensional computer aided engineering design systems are recognized as having limitations in comparison with the alternative three-dimensional techniques of solid modelling. The mathematically sounder approach of solid modelling permits far greater integration between the activities of functional design, design analysis and manufacturing. However, the existing methods of specifying design geometry within typical solid modelling systems are deficient in that they relate more to the mathematical needs of the computer system than they do to the needs of the designer. CAPE-LUT (Computer Aided Production Engineering-Loughborough University of Technology) is a prototype system which provides a machining analogy so that geometric and manufacturing ideas can be expressed through familiar engineering terminology, to provide detail designs and outline process plans. CAPE-LUT is an experimental vehicle only and the system has been used to investigate the hypothesis that a 'manufacturing features' approach to design and manufacture is easy to learn, accurate and fast in use, and acceptable to practising designers and manufacturing engineers. This paper describes the experimental work, which provides statistical evidence that the manufacturing features method is significantly easier to learn than a similar CAD system that has a purely geometric interface. It is also shown that CAPE-LUT performed well when used by experienced subjects and was acceptable to a large number of practising engineers.     

Form tolerance-based measurement points determination with CMM

In an intelligent manufacturing environment, computer aided inspection (CAI) provides a critical role in closing the computer aided design (CAD) to computer aided manufacturing (CAM) loop. A coordinate measuring machine (CMM) is often used as a measurement tool in a mechanical part manufacturing environment. Feature-based measurement (FBM) with CMM plays an important role in the concurrent engineering environment (Fig. 1) (Yau and Menq, 1993). It measures a part and feedbacks the results to the concurrent control center to modify related process attributes. Feature-based computer aided inspection (CAI) systems define various measurement attributes for different features (Jacobohn et al., 1990). Part of the system determines the number of measurement points for a feature. In this research, a computer aided feature-based statistical concept is used to calculate sufficient measurement points for a feature. Circular and cylindrical parts are used to demonstrate the proposed methodology for determining the number of measurement points. The results show that the measurement error is significantly lower with the proposed method in determining the number of measurement points as compared to the method commonly used with a CMM. The proposed methodology is also computerized for on-line applications.     

A STEP-compliant process planning system for CNC turning operations

Over the last 50 years, there have been many significant enhancements in computer aided systems which have influenced the CNC technology. One area that can be considered as a bottleneck to these CNC enhancements, and in particular to interoperability in CNC manufacturing is G&M part programming (ISO 6983). To overcome this bottleneck, the new standard ISO 14649, known as STEP-NC, is being developed to provide detailed information on component design, process planning and machining strategies to manufacture parts for the next generation of intelligent CNCs. This standard forms the basis of a new paradigm shift in the CNC domain to support digital modelling of CNC manufacturing resources. The research in this paper aims to identify major issues and develop new software tools to demonstrate the feasibility of interoperable CNC manufacturing based on STEP-NC. Besides the literature review on recent research and development on STEP-NC, this paper proposes a Process Planning System (PPS) with surface roughness chosen as the process planning objective. PPS consists of five modules: program reader, process planner, STEP-NC CAD viewer, STEP-NC CAM viewer and program writer. The reader is responsible for interpreting the geometry and the manufacturing data from a STEP-NC text file into a stored data list. The process planner uses this data list and enables users to evaluate surface roughness based on a mathematical model. Through the STEP-NC CAD viewer, the part geometry can be shown and via the STEP-NC CAM viewer the toolpath can be verified. Finally, the writer converts the stored STEP-NC data of the system into an updated STEP-NC file. An example case study component is used to demonstrate the PPS and show the interfacing of the STEP-NC data.     

Automated restoration of engineering drawings into a CAD data base

With the increasing use of computers in the area of design and manufacture, a major problem being faced by the industry today is that of getting existing product information in the form of paper drawings into a suitable computer data base. This paper presents techniques for preprocessing and vectorizing scan digitized images of engineering drawings for automatically transferring the resulting data to commercially available CAD/CAM systems. The preprocessing steps include noise removal, void filling, image segmentation, line thinning and contour extraction. Algorithms for raster-to-vector conversion capable of recognizing and fitting straight-line segments, circles, arcs, and conic sections are presented along with results obtained from actual machine drawings.     

An agent-oriented approach to resolve scheduling optimization in intelligent manufacturing

Agent technology is considered as a promising approach for developing optimizing process plans in intelligent manufacturing. As a bridge between computer aided design (CAD) and computer aided manufacturing (CAM), the computer aided scheduling optimization (CASO) plays an important role in the computer integrated manufacturing (CIM) environment. In order to develop a multi-agent-based scheduling system for intelligent manufacturing, it is necessary to build various functional agents for all the resources and an agent manager to improve the scheduling agility. Identifying the shortcomings of traditional scheduling algorithm in intelligent manufacturing, the architecture of intelligent manufacturing system based on multi-agent is put forward, among which agent represents the basic processing entity. Multi-agent-based scheduling is a new intelligent scheduling method based on the theories of multi-agent system (MAS) and distributed artificial intelligence (DAI). It views intelligent manufacturing as composed of a set of intelligent agents, who are responsible for one or more activities and interacting with other related agents in planning and executing their responsibilities. In this paper, the proposed architecture consists of various autonomous agents that are capable of communicating with each other and making decisions based on their knowledge. The architecture of intelligent manufacturing, the scheduling optimization algorithm, the negotiation processes and protocols among the agents are described in detail. A prototype system is built and validated in an illustrative example, which demonstrates the feasibility of the proposed approach. The experiments prove that the implementation of multi-agent technology in intelligent manufacturing system makes the operations much more flexible, economical and energy efficient.     

Design of a STEP compliant system for turning operations

The changing economic climate has made global manufacturing a growing necessity over the last decade, forcing companies from East and West to collaborate beyond geographic boundaries in the design, manufacture and assembly of products. The ISO 10303 and ISO 14649 Standards (STEP and STEP-NC) have been developed to introduce interoperability into manufacturing enterprises so as to meet the challenges of responding to production on demand. This paper describes and illustrates a STEP compliant CAD/CAPP/CAM System for the manufacture of rotational parts on CNC turning centers. The information models to support the proposed system together with the data models defined in the ISO 14649 standard used to create the NC programs are also described. A structured view of a STEP compliant CAD/CAPP/CAM system framework supporting the next generation of intelligent CNC controllers for turn/mill component manufacture is provided. Finally a proposed computational environment for a STEP-NC compliant system for turning operations (SCSTO) is described. SCSTO is the experimental aspect of the research and is supported by information models that and have been constructed using a structured methodology and object-oriented methods. SCSTO was developed to generate a Part 21 file based on machining features to support the interactive generation of process plans utilizing feature extraction. A case study component has been developed to prove the concept of using the milling and turning parts of ISO 14649 to provide a turn-mill CAD/CAPP/CAM environment.     

利用用户定义特征实现基于约束设计

提出了基于约束的用户定义特征（User Defined Feature,UDF)定义与比实例化的通用机制及基于约束的特征库管理,并应用于国产CAD／CAM软件金银花（Lonicera)系统,以航空发动机转子为例,建立了转子特征库,对系统功能进行了验证。该项工作既为详细设计阶段考虑装约束和制造约束提供了方便,提高了设计效率,也为将用户定义特征与产品功能相联系、以支持计算机辅助概念设计打下了基础。     

电子计算机辅助技术在机械领域的应用

当今社会计算机应用已经深入了各行各业,计算机在机械领域的应用给机械制造业带来了巨大变化.电子计算机辅助技术(CAD)是当前设计单位的热门话题之一,如何改造传统的设计方法建设现代化的设计,从科技进步中获得经济效益,是一个很值得讨论的问题.CAD技术作为电子信息技术的一个重要组成部分,是促进科研成果的开发和转化,促进传统产业和学科的更新和改造,实现设计自动化,增强企业及其产品在市场上的竞争能力,加速国民经济发展和国防现代化的一项关键性技术.CAD技术基础理论的每次重大进展,无一不带动了CAD/CAM/CAE整体技术的提高以及制造手段的更新.技术发展,永无止境.没有一种技术是常青树,CAD技术一直处于不断的发展与探索之中.正是这种此消彼长的互动与交替,造就了今天CAD技术的兴旺与繁荣,促进了工业的高速发展.今天,越来越多的人认识到CAD是一种巨大的生产力,不断加入到用户行列之中.本文利用电子计算机辅助设计软件完成机械零件设计的全过程,通过设计机械零件体会CAD在机械和航空设计领域的应用以及不足.本文最后还谈了CAD技术在中国企业应用的不足和CAD技术的发展趋势.     

Viewer-centered geometric feature recognition

Computer aided design (CAD) and computer aided manufacturing (CAM) systems are now indispensable tools for all stages of product development. The flexibility and ease of use of these systems has dramatically increased productivity and quality of product while reducing lead times. These advances have been largely achieved by automating individual tasks. At present, these islands of automation are poorly linked. One reason for this is that current computer systems are unable to extract geometric and topological information automatically from solid models that is relevant to the down-stream application. In other words, feature information.The objective of the research reported in this paper was to develop a more generic methodology than heretofore, in order to find the generic protrusion and depression features of a CAD model. The approach taken is one relying on a more human type of analysis, one that is viewer-centered as opposed to the object-centered approach of most previous research in this area. The viewer-centered approach to feature recognition described is based on a novel geometric probing or tomographic methodology. A five-step algorithm is described and then applied to a number of components by way of illustration.     

Design of the database for CAD based on group technology

An important part of integrated CAD/CAPP/CAM is represented by the database in which all the information and data relevant for the design, planning and manufacturing of a component are available to the designer. The database must thus include relevant data about the geometrical primitives, materials, surfaces, tolerances, etc.This paper reports on the design of a database to be used in CAD/CAPP/CAM with particular reference to GT principles. The data required in the CAD process are strongly structured, so that their computer representation actually yields a structural model of the component. The elements which form the component model are parameterized shape primitives generating the matrix of the primitives for forming rotational and non-rotational components. The organization of their data and the communication between the designer and the database are discussed in detail. In this context a solution is proposed which enables the designer not only to draft a component by means of a computer, but, at the same time, to classify the component into a part family using a pattern recognition method for computer-aided GT classification.     

试述CAD技术在美术工业造型设计中的应用

当今社会计算机应用已经深入了各行各业,计算机在美术工业造型领域的应用给美术工业造型业带来了巨大变化.电子计算机辅助技术(CAD)是当前设计单位的热门话题之一,如何改造传统的设计方法建设现代化的设计,从科技进步中获得经济效益,是一个很值得讨论的问题.CAD技术作为电子信息技术的一个重要组成部分,是促进科研成果的开发和转化.促进传统产业和学科的更新和改造,实现设计自动化,增强企业及其产品在市场上的竞争能力,加速国民经济发展和国防现代化的一项关键性技术.CAD技术基础理论的每次重大进展,无一不带动了CAD/CAM/CAE整体技术的提高以及制造手段的更新.技术发展,永无止境.没有一种技术是常青树,CAD技术一直处于不断的发展与探索之中.正是这种此消彼长的互动与交替.造就了今天CAD技术的兴旺与繁荣.促进了工业的高速发展.今天,越来越多的人认识到CAD是一种巨大的生产力,不断加入到用户行列之中.本文利用电子计算机辅助设计软件完成工业造型零件设计的全过程,通过设计工业造型零件体会CAD在工业造型设计领域的应用以及不足.     

A product modeling system for constructing intelligent CAD and CAM systems

It is essential for the achievement of intelligent manufacturing systems to properly encode manufacturing knowledge in computer systems. We propose a product modeling system that is a framework for representing and utilizing models of both design objects and design tasks. The key concept in the framework is that of constraint. Several prototypical CAD/CAM applications constructed on the framework are shown.