基于Pro/ENGINEER的注塑模电极工程图模块设计

针对所开发的注塑模电极CAD系统,利用Pro/E提供的二次开发工具Pro/TOOLKIT和MFC对话框技术,在Visual C++ 6.0编译环境下,对Pro/E的工程图模块进行二次开发,实现了注塑模电极工程图的自动生成,提高了注塑模电极工程图的设计效率。     

Intelligent Programming of CNC Turning Operations using Genetic Algorithm

CAD/CAM systems are nowadays tightly connected to ensure that CAD data can be used for optimal tool path determination and generation of CNC programs for machine tools. The aim of our research is the design of a computer-aided, intelligent and genetic algorithm(GA) based programming system for CNC cutting tools selection, tool sequences planning and optimisation of cutting conditions. The first step is geometrical feature recognition and classification. On the basis of recognised features the module for GA-based determination of technological data determine cutting tools, cutting parameters (according to work piece material and cutting tool material) and detailed tool sequence planning. Material, which will be removed, is split into several cuts, each consisting of a number of basic tool movements. In the next step, GA operations such as reproduction, crossover and mutation are applied. The process of GA-based optimisation runs in cycles in which new generations of individuals are created with increased average fitness of a population. During the evaluation of calculated results (generated NC programmes) several rules and constraints like rapid and cutting tool movement, collision, clamping and minimum machining time, which represent the fitness function, were taken into account. A case study was made for the turning operation of a rotational part. The results show that the GA-based programming has a higher efficiency. The total machining time was reduced by 16%. The demand for a high skilled worker on CAD/CAM systems and CNC machine tools was also reduced. Received: September 2004 / Accepted: September 2005     

关于叶轮集成化智能CAM系统的研究

针对叶轮五坐标ＣＡＭ技术，本文在统一的产品信息模型基础上， 运用智能工程技术，建立了一个并行分层式集成化ＣＡＭ系统，此系统可有效地解决叶轮零件的图形输入，几何设计、叶片及叶轮的造型、曲线及曲面求交、加工刀心轨迹的求解等，并以ＤＮＣ方式控制数控机床进行加工，实现了软硬件的集成。     

Automatic and a priori refinement of three-dimensional meshes based on feature recognition techniques

This work presents the general evolution of CAD/CAM systems for a better integration of all functions involved in the design and manufacturing process of mechanical parts (simultaneous engineering). We are proposing here an approach of the automatic three-dimensional mesh generation problem featuring a pre-optimization scheme based on the “a priori” evaluation of a dual geometric model (CSG–Exact B-Rep) in order to identify, directly and automatically, geometric features causing stress concentration. We provide more precise knowledge on how geometric features are identified and used in order to calculate a nodal density field across the parts that is more interesting for analysis or representation purposes.     

An integrated intelligent machining system for axisymmetric parts using PC-based CAD and CAM software packages

Machining process planning involves the formation of a set of directions describing the machining operations required to transform raw stock into a finished part. Conventional process planning, performed manually, relies on the knowledge and competence of an experienced process planner and tends to be time consuming and error prone. In the past two decades, much effort has been spent on improving process planning by utilizing the power of a computer to emulate the capabilities of an experienced planner. During the same period, computer-aided design (CAD) and computer-aided manufacturing (CAM) software has been developed to enhance design productivity and to assist the NC code generation facets of the machining process. The entire planning process may be automated be integrating CAD and CAM using computer-aided process planing (CAPP). The research described in this paper outlines the design and development of an intelligent CAPP system integrating two commercial CAD and CAM software packages, Autocad and Mastercam.     

HSC-1.1:A USEFUL TOOL FOR INJECTION MOLDING

An integrated CAD/CAE/CAM system, HSC--1.1, is described in the paper. HSC--1.1integrates surface modeling, mold design, technological simulations and NC machining into a full CAD/CAE/CAM system with data exchange from one module to another. The practice shows that HSC--1.1 is a useful tool for injection molding and can assist engineers in reducing mold cost and improvingmold quality.     

Automatic Narrow-Deep Feature Recognition for Mould Manufacturing

There usually exist narrow-long-deep areas in mould needed to be machined in special machining.To identify the narrow-deep areas automatically,an automatic narrow-deep feature (NF) recognition method is put forward accordingly.First,the narrow-deep feature is defined innovatively in this field and then feature hint is extracted from the mould by the characteristics of narrow-deep feature.Second,the elementary constituent faces (ECF) of a feature are found on the basis of the feature hint.By means of extending and clipping the ECF,the feature faces are obtained incrementally by geometric reasoning.As a result,basic narrow-deep features (BNF) related are combined heuristically.The proposed NF recognition method provides an intelligent connection between CAD and CAPP for machining narrow-deep areas in mould.     

An Internet-based intelligent design system for injection moulds

The rapid growth of Internet and information technologies in recent years provides a solution to support and facilitate collaborative product developments among different geographically distributed enterprises. An effective and feasible tool to aid the collaborative development of injection moulds can be realized by developing an Internet-based mould design system as one of the modules of a collaborative product development system. This paper presents a prototype Internet-based intelligent design system for injection moulds. The architecture of the system consists of an interactive KB mould design system embedded in an Internet environment. A Java-enabled solution together with artificial intelligence techniques is employed to develop such a networked interactive CAD system. In this system, the computational module, the knowledge base module and the graphic module for generating mould features are integrated within an interactive CAD-based framework. The knowledge base of the system would be accessed by mould designers through interactive programs so that their own intelligence and experience could also be incorporated with the total mould design. The approach adopted both speeds up the design process and facilitates design standardization which in turn increases the speed of mould manufacture. A practical case study is presented to illustrate the operations of the Internet-based mould design system.     

THE OBJECT-ORIENTED INTELLIGENT PROGRAMMING IN CAD/CAM

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Open architecture of CNC system research based on CAD graph-driven technology

Based on CAD graph-driven technology, a kind of novel open architecture CNC system is put forward and designed together with the key hardware “PC+PMAC controller”. The intelligent CNC system software including several function modules is developed under Visual C++6.0 environment. Graphic feature identification and geometric parameter extraction from CAD-part-drawing saved as DXF format are performed to control the relative motion between cutting tool and part. The ant-colony algorithm is applied to auto-optimize the cutting tool paths in machining process. The experiment results of a plane engraving machining example show that the proposed method is feasible, and the entire machining process no longer needs NC programming. The efficiency of CNC machining is improved greatly, and the true intelligent CNC machining can be realized when the advanced programming technologies are integrated in one system according to the proposed conception.     

Integrated manufacturing features and Design-for-manufacture guidelines for reducing product cost under CAD/CAM environment

The main contribution of the work is to develop an intelligent system for manufacturing features in the area of CAD/CAM. It brings the design and manufacturing phase together in design stage and provides an intelligent interface between design and manufacturing data by developing a library of features. The library is called manufacturing feature library which is linked with commercial CAD/CAM software package named Creo Elements/Pro by toolkit. Inside the library, manufacturing features are organised hierarchically. A systematic database system also have been developed and analysed for each feature consists of parameterised geometry, manufacturing information (including machine tool, cutting tools, cutting conditions, cutting fluids and recommended tolerances and surface finishing values, etc.), design limitations, functionality guidelines, and Design-for-manufacture guidelines. The approach has been applied in two case studies in which a rotational part (shaft) and a non-rotational part are designed through manufacturing features. Therefore, from manufacturing feature library a design can compose entirely in a bottom-up manner using manufacturable entities in the same way as they would be produced during the manufacturing phase. Upon insertion of a feature, the system ensures that no functionality or manufacturing guidelines are violated. The designers are warned if they attempt to include features that violate Design-for-manufacture and Design functionality guidelines. If a feature is modified, the system validates the feature by making sure that it remains consistent with its original functionality and Design-for-manufacture guidelines are re-applied. The system will be helped the process planner/manufacturing engineer by automatically creating work-piece data structure.     

A novel spark erosion technique for the fabrication of high aspect ratio micro-grooves

Micro groove is an important geometrical feature of components used in microsystem technology (MST). Straight micro grooves are the predominant features in microsystem components such as micro heat exchangers and diffraction gratings. Micro Electrical Discharge Machining (micro EDM) is a complementary microfabrication technique adopted from the conventional EDM machining process for the purpose of micro machining. Using micro EDM it is possible to machine all electrically conductive materials irrespective of their hardness. High aspect ratio microgroove machining for length as high as 20 mm is a formidable task for the conventional micro EDM. In the present work, a novel spark erosion technique has been described wherein a graphite foil has been used instead of the traditional pin shaped tool electrode, for the purpose of making straight grooves. In a single setup microgroove of 20 mm length and an aspect ratio of about 2.3 has been achieved on hardened tool steel by this technique. This process is further refined by using the gravitational effect for the effective debris removal, which has improved the aspect ratio to about 8.Accepted: September 2003     

Tool electrode geometry and process parameters influence on different feature geometry and surface quality in electrical discharge machining of AISI H13 steel

Electro discharge machining process (EDM) is frequently used when machining of high complex and accurate features is required. Indeed, it is specially recommended for hard materials and micro-machined features. However, due to the process nature, there is still incomprehension on process parameters influence at the final quality features, ending up by lower productivity and quality ratios. On the other hand, fashioning and re-shaping of required electrodes for each feature are time consuming phases and the number of stored electrodes is very high. Therefore, in order to increase the global EDM process productivity, quality and flexibility, standardized simple electrode shapes, capable to machine different features, must be found. This study presents the influence of the main EDM process parameters and different tool geometries on basic process performance measures. A set of designed experiments with varying parameters such as pulsed current, open voltage, pulse time and pulse pause time are carried out in H13 steel using different geometries of copper electrodes. In addition, material removal rate , surface roughness and different dimensional and geometrical micro-accuracies are analyzed through statistical methods. Results help to select appropriate EDM process parameters to machine parts depending on product requirements.     

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.     

Product design logic for an intelligent product modelling system

Recent research in CAD systems has been conducted to realize intelligent processing. Several CAD systems and product modelling systems have been developed using AI techniques. However, in order to develop more intelligent CAD systems, the design logic which connects the functional requirement to the geometric and the technological information of the designed product must be evaluated.

A product model used in such intelligent CAD systems has to include not only the geometric and the technological information of the product but also the designer's thought process which explains the design logic.

Design logic is generally divided into two parts. One is the generalized design logic which is commonly used in the conceptual design of mechanical products. The other is the product specified design logic which is used in the fundamental and detailed design phase. Different logic is applied to each product. This type of design logic is often used in modification design and compilation design, where the dimensions of parts have to be modified according to different functional requirements. When the dimensions and accuracies of the products are defined in connection with the functional requirements through design logic, the CAD system can automatically make decisions according to the given requirements. In this paper, suitable presentation formats and processing functions for these two types of design logic are discussed.

The importance of design logic in product modelling is proven through several case studies in this paper. As a conclusion, the intelligent product modelling system is developed, which should expedite the progress of design automation in the near future. In conceptual design, the design logic is processed in the modelling system and the product structure, with the technological information decided automatically from the functional requirement. Automation in the detailed design phase is also facilitated by the modelling system using the product specified design logic in the product model.     

High aspect ratio meso-scale parts enabled by wire micro-EDM

Micro-electro discharge machining (EDM) is a subtractive meso-scale machining process. The Agie Excellence 2F wire micro EDM is capable of machining with a 25 micron diameter wire electrode and positioning the work piece to within ±1.5 microns. The over-burn gap can be controlled to within 3 microns to obtain a minimum feature radius of about 16 microns while achieving submicron surface finish and an imperceptible recast layer. For example, meso-scale gears that require vertical sidewalls and contour tolerances to within 3 microns can be wire EDMed into a variety of conductive materials. Material instabilities can affect the dimensional precision of machined meso-scale parts by material relaxation during the machining process. A study is done to investigate the machining performance of the wire micro EDM process by machining a high aspect ratio meso-scale part into a variety of metals (e.g. 304L stainless steel, Nitronic 60 Austentic Stainless, Beryllium Copper, and Titanium). Machining performance parameters such as, profile tolerance, perpendicularity, and repeatability are compared for the different materials. Pertinent inspection methods desirable for meso-scale quality assurance tasks are also evaluated. Sandia National Laboratories is developing meso-scale electro-mechanical components and has an interest in the assembly implications of piece parts fabricated by various meso-scale manufacturing processes. Although the wire EDM process is typically used to fabricate 2½ dimensional features, these features can be machined into a 3 dimensional part having other features such as hubs and chamfers to facilitate assembly.     

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.     

An integrated implementation for product design

This paper represent an integrated implementation to shorten the product development cycle. The developed system uses machine vision techniques to automate the creation of CAD models for existing parts of prototypes. It extracts the manufacturing features based on the created CAD database and the tolerances that are to be added to the created CAD dabatase for CAD/CAM practice and concurrent analysis. The geometric features are organized in a database which can be imported to an automated process planning and cost estimation system. This integrated implementation is capable of providing manufacturing feedback during the product development stage. This paper outlines the development of the vision system, the creation of the CAD model, and the design of the database.     

基于UG的五轴数控机床加工仿真

目前多数五轴数控机床仿真系统,一般只提供二维的动画仿真,而且仿真系统的几何造型功能十分有限,零件和机床模型需要在其他CAD软件中进行建模,然后导人数控仿真系统。由于文件格式的转化,零件的CAD模型将会产生误差,降低了仿真精度。该文利用UGCAD／CAM软件造型功能建立五轴数控机床和零件模型,读取数控代码对机床各部件进行三维运动仿真,并对加工过程中机床运动部件之间的干涉及工件过切进行检查,建立干涉实体,为刀具轨迹的修改提供依据,同时免除了文件格式的转化产生的误差。