A Fast Interference Checking Algorithm for Automated Fixture Design Verification

Fixtures are tooling devices used to locate, support and hold workpieces during a manufacturing process. The major purpose of a computer-aided fixture design (CAFD) system is to provide a fixture design based on fixturing principles and workpiece information. Interference checking between the machining tool and fixture units, as well as between fixture units, is one of the important functions of automated fixture design. This paper presents a fast interference checking algorithm for automated modular fixture design validation. It is based on the study of the geometric characteristics of modular fixture components and the machining tool. The fixture component model is simplified into a 2D contour model with height information. The tool-path model is represented by a moving dot for 3-axis operations, or a moving line segment in 5-axis operations, as the fixture component model is different from the popular collision detection procedure using swept volume and is more efficient for fixturing verification. Application of this method will greatly reduce the computation complexity for fixturing interference checking. The method is implemented with a CAFD system. An example is given at the end of the paper.     

FIX-DES: A computer-aided modular fixture configuration design system

This paper presents a computer-aided modular fixture configuration design system: FIX-DES. When fixturing requirements are specified as locating/clamping surfaces and points, a fixture configuration will be automatically generated by

1. Selecting fixture elements from a fixture element database to form fixture units based on fixture element assembly relationships.
2. Placing the fixture units and elements into position on a baseplate while the fixturing requirements and assembly relationships (e.g. hole alignments) are maintained.

The fixture element assembly relationships can be established automatically when the geometric models and fixturing functions of the fixture elements are specified so that the FIX-DES system can be applied easily to different fixture systems. The system also provides the interactive design and design modification functions for human expert involvement. The system was developed with core programs in C and C++ and interface programs in a specific CAD environment. The system has been successfully applied in industry and can be transferred easily to other CAD systems. The overall structure of the FIX-DES system is introduced in the paper. The development of the automated fixture configuration design (AFCD) functions are presented in detail. Finally a fixture configuration design example is given to illustrate the application of the system.     

Development of Automated Fixture Planning Systems

Fixturing is an important manufacturing activity. The computeraided fixture design technique is being rapidly developed to reduce the lead time involved in manufacturing planning. An automated fixture configuration design system has been developed to select automatically modular fixture components and place them in position with satisfactory assembly relationships In this paper, an automated fixturing planning system is presented in which fixturing surfaces and points are automatically determined based on workpiece geometry and operational information. Fixturing surface accessibility, feature accuracy, and fixturing stability are the main concerns in the fixture planning. The system development, the fixture planning decision procedure, and an implementation example are presented in the paper.     

基于微机的成组夹具计算机辅助设计系统

介绍的成组夹具计算机辅助设计系统（ＧＦＣＡＤ）,是在ＢｏｒｌａｎｄＣ＋＋３．１、Ｆｏｘｂａｓｅ＋２．１环境下和ＡｕｔｏＣＡＤ１２．０绘图软件的基础上开发而成的。它由夹具结构设计,标准件特征造型,标准件图形文件自动生成及图形处理等四大模块组成。该系统是面向夹具设计师的。     

汽车覆盖件焊装夹具虚拟设计参数库的开发

汽车焊装夹具的设计直接影响到汽车车身的制造质量和开发周期 ,计算机辅助夹具设计技术逐渐得到重视。本文通过采用模块设计和参数化设计技术 ,研究车身薄板零件焊装夹具的设计特征和设计过程 ,建立了汽车焊装夹具设计分类系统 ,开发出基于实例的汽车虚拟焊装夹具设计参数化零件库。采用该系统将减少焊装夹具的静动态调试时间 ,提高夹具设计水平 ,缩短车身开发周期     

基于PLC的自动化夹具教学实验台的设计与实现

在分析现有夹具教学实验台的实验原理、实验方式以及存在问题的基础上,设计制造了一种新型的基于PLC的自动化夹具教学实验台系统,该系统将夹具本体、数字控制、气压控制、液压控制有机结合在一起,形成一个机电液气一体的教学实验台,学生通过实验台可以掌握夹具的工作原理、结构特点、设计要点,并可在实验台上开展创新的夹具实验,进一步的加深对夹具的认识。     

基于ASP的夹具远程设计系统的开发

分析了传统夹具设计方式的局限性,指出网络技术对现代夹具设计的影响和建立夹具远程设计系统的必要性。介绍了夹具远程设计系统的结构和系统开发的主要技术方法,并给出了远程设计计算实例。     

工件定位方案的自动规划与定位误差分析

工件定位方案的自动规划是智能化夹具设计过程的重要组成部分。构建了一个定位方案规划系统,对基于知识的工件定位表面的自动选择、定位点位置的确定和优化以及夹具的综合定位误差进行了分析。     

计算机辅助组合夹具设计系统的研究

讨论了夹具ＣＡＤ的现状、发展历史、生产的需求以及夹具ＣＡＤ系统的类型。介绍了由本文作者开发的组合夹具ＣＡＤ系统的实例，提出了组合夹具结构自动生成的原理和模型。     

基于CATIA平台的夹具快速设计与制造系统的构建

重点研究CATIA在专用夹具设计及制造过程中的应用问题。夹具设计涉及到数值计算 ,图形绘制等一些算法问题。CATIA在解决这类问题时显示出其优越性。关键是研究如何在CATIA环境下建立专用夹具设计、制造快速响应系统的总体结构 ,特别是在如何建立专用夹具元件库及夹具可行性分析等方面作了一些研究。对有关夹具相似性比较的推理方法也作了一些探讨。     

基于偏差传递的二维多工位装配夹具系统公差可行稳健设计

提出一种基于偏差传递的二维多工位装配夹具系统公差可行稳健设计方法。分析二维多工位装配尺寸偏差传递关系,建立由定位销和零件定位孔(槽)公差引起夹具定位偏差的偏差流状态空间模型。采用数论网格方法对定位销和零件定位孔(槽)公差进行采样,将得到的公差样本代入夹具定位偏差模型,求得夹具定位偏差样本空间,将夹具定位偏差作为状态空间模型的输入偏差,提出基于状态空间模型的二维多工位装配成功率计算方法。继而应用Taguchi正交试验直观分析方法,分析得到影响装配成功率的主要因素即夹具系统定位销副关键公差,运用回归正交组合设计拟合得到二维多工位装配成功率与夹具系统定位销副关键公差的响应面模型。以定位销、零件定位孔(槽)制造成本所构成的装配成本最小化为目标,二维多工位装配成功率为约束,建立二维多工位装配夹具系统定位销和零件定位孔(槽)公差可行稳健设计模型。以汽车车身地板二维三工位装配为例,建立其公差可行稳健设计模型并对该模型进行计算与分析,结果表明在装配成本增幅较小的情况下,采用稳健约束后可显著提高公差设计的可行稳健性。该方法为二维多工位装配夹具系统公差稳健设计提供了一种新途径。     

机床夹具精度基准平面体系控制法的研究

在夹具精度设计中,应用本研究提出的夹具精度三基准辅助平面体系控制法,有利于实现项目完整、指标合理、易于规范化设计和计算机辅助设计。该方法以夹具复合体为设计对象,以工件结构和加工精度要求为目标,以加工刀具和机床安装基准面为参考体,利用三个基准辅助平面来确定夹具精度控制项目:第Ⅰ辅助基准平面为平行于刀具速度方向、与机床工作台(面)对应的夹具安装基面;第Ⅱ辅助基准平面(线)通过刀具(或夹具)中心,并垂直于第Ⅰ基准平面;第Ⅲ辅助基准平面通过夹具某点,并垂直于第Ⅰ和第Ⅱ辅助基准平面。     

柔性化夹具静动态特性分析及拓扑优化

针对汽车发动机缸盖、变速箱阀体全自动化混合生产线,设计柔性化夹具来满足CNC高精密加工以及快速换产的要求。建立夹具系统三维模型,并利用ANSYS对夹具系统在不同加工工况载荷下进行静态性能分析;从分析结果判断出影响夹具性能的关键结构,并对其进行拓扑优化设计,实现夹具整体减重39.25 kg。然后对改进后夹具模型进行验证分析,发现最大变形量减少为0.0045199 mm,满足设计指标0.005 mm;最后,对现有夹具系统进行模态实验和CAE模态分析,发现夹具系统在Z向受到低频激振力时,容易发生共振,该频段为70 Hz?110 Hz,在加工过程中需要控制刀具加工频率避免发生共振。     

A case-based reasoning approach for design of machining fixture

Appropriate fixture design could lower process time, lower cost, and improve the quality of products. This paper proposes a case-based reasoning (CBR) method, with improved indexing and retrieving approaches which are critical issues in machining fixture design systems. A case storage for fixture design case indexing approach is developed so that the database is constructed into two levels—to manage and categorize numerous related fixture designs. The data includes existing workpieces and associated fixture planning and unit depository as solutions. Based on this approach, a CBR method with a two-step case retrieval is presented. The objective is to improve searching results in database for machining fixture design. In this CBR-based fixture design method, the appropriate workpiece in the first level of database by using design requirement is found. Then, the proper conceptual fixture design can be achieved by retrieving related fixture case from the second level. This method facilitates the fixture designing by means of referencing past design cases to generate a conceptual fixture design quickly and easily. It also helps in the finishing design by suggesting some alternative fixture cases. Finally, several case studies are used to validate and present the applicability and usability of the proposed approach.     

Development of an automated fixture set-up system for inspection

This paper presents an automated fixture set-up for inspection. The system comprises a workplace with magazines, locators and a baseplate. An articulated robot, the SCORBOT-ER VII is used to automate the system. A C-program is developed and used to execute robot arm movements based on user input. The C-program also establishes locating postions for a rectangular workpiece and determines the set-up of the locating fixtures via points. The program is therefore a useful interface to other small-scale expert systems for fixture design and graphical simulators. The set-up of the fixtures can be performed for other complex shapes if locating points are known, and input into the robot controller using the C-program.     

一种孔系组合夹具夹紧装置构形设计方法

介绍一种针对棱柱形工件的孔系组合夹具夹紧装置的自动构形方法。首先确定工件的夹紧区域并离散化,然后根据工件的形状确定夹紧装置的个数,进而确定候选夹紧方案,并提出夹紧方案的质量评价标准。最后通过实例验证上述方法的可行性和精确性。     

基于B/S模式的夹具设计系统的研究

介绍了一种基于B／S模式的夹具系统设计方法，分析了系统结构的特点，主要模块与功能，开发关键技术。此系统实现了各种设计计算和快速夹具设计，提高了夹具设计资源的共享程度，对夹具设计的效率和精度有很重要的作用。     

基于.NET的夹具元件图形库系统设计

针对机床夹具设计的结构,构建了夹具元件图形库体系结构。利用网络技术、数据库技术、.NET技术以及AutoCAD/MDT二次开发机制,提出了基于.NET的夹具元件图形库系统的实施方案。实现了异地夹具资源信息共享,为机械企业的夹具设计人员提供一个方便的辅助工具。     

基于功能特征结构映射的夹具设计模型与方法

为实现夹具设计的智能化,基于功能论的设计方法,通过对夹具的功能进行分析和分解,研究了夹具功能的表达和夹具的设计过程,建立了基于功能特征映射模型的夹具设计过程和方法。构建了夹具的功能模型,提出用特征作为夹具功能和结构的中介,建立了功能-特征-结构的映射模式。在对夹具设计中的约束进行分析的基础上,总结了夹具各子功能的备选特征集,运用模糊映射的理论实现夹具功能到特征和特征到结构的映射,得到夹具的结构方案。最后,用钻模设计进行了实例验证,证明了该方法的可行性和有效性。     

Selection of preliminary locating and clamping positions on a workpiece for an automatic fixture design system

This paper focuses on the development of heuristic algorithms for selecting the locating and clamping positions on an automatic fixture configuration for a given workpiece for an automatic fixture design (AFD) system. It discusses several issues regarding (i) an informationally complete product model, and (ii) the development of necessary computational modules coupled with a knowledge based system to reason about the workpiece's geometric characteristics for determining the locating and clamping positions. The motivation of the work is to develop a fixturing subsystem as an integral part of the complete CIM environment. A prototype AFD system has been completed in the object oriented programming platform of Wisdom's Concept Modeller. It has used several geometric reasoning mechanisms based on the traditional fixture design principles, and on the principles of collision-free assembly. The system exploits the power of Wisdom's advanced geometric modelling (AGM), and it implements the basic architecture of the proposed knowledge based fixture design system.