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.     

Experimental investigation of the performance of a reconfigurable fixturing system

A reconfigurable fixturing system has been developed for computer-integrated assembly environments. The fixturing system employs a number of fixture modules that are set-up, adjusted and changed automatically by the assembly robot without human intervention. A commercially available computer-aided design (CAD) package with the help of a dedicated software program is used for the design, analysis, and verification of the fixture layout. The robot program for setting-up, adjusting, and dismantling the designed fixture is generated automatically. This paper presents and discusses the accuracy of such a reconfigurable fixturing system in view of the off-line programming techniques. The experimental techniques to measure the accuracy and repeatability for setting-up the fixture are presented. The measured results of the robot positioning various types of locating fixture modules are presented and compared with the intended position settings. From the comparison, the accuracy that is to be expected from such an approach to fixturing and measures for improvement are discussed. The cycle times involved in setting-up the fixture modules are also presented and analysed. These results provide an initial guide for manufacturing industries interested in employing such systems in their computer-integrated assembly environment.     

Computer-Aided Fixture Design Verification. Part 1. The Framework and Modelling

Computer-aided fixture design (CAFD) techniques have been advanced rapidly so that fixture configurations can be generated automatically, for both modular fixtures and dedicated fixtures. Computer-aided fixture design verification (CAFDV) is the technique for verifying and improving existing fixture designs. In this paper, the framework of CAFDV is introduced based on two models, i.e., geometric and kinematic models. The fixturing tolerance and stability verification will be presented in separate papers.     

An expert system for fixturing design for face milling using modular fixture

The research objective of this paper is to develop an expert system for a modular fixture. We provide a complete fixturing procedure analysis for workpieces with different shapes such as L, I, T, and U types. In this system AutoCAD is used to draw the workpiece; then the data for points, lines, and faces are dealt with. Using the knowledge presentation method, the clamping position of the modular fixtures, the kinematics constraint balance and the fixture and cutting forces are determined. Integer programming is used to arrive at an optimal arrangement. In addition, the system provides a learning concept incorporating knowledge from experience and heuristic rules to enable repeated self-learning to compensate for the lack of knowledge. Finally, some examples are demonstrated.     

A literature survey of fixturedesign automation

This paper gives a review of fixture-design research, most of it done in the 1980s. The major topics of the review are the fixturing principles (supporting, locating and clamping), automated fixture design (configuration, assembly and verification), and fixture hardware design (dedicated, modular and electric/magnetic types).     

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.     

组合夹具计算机三维智能组装系统

将CAD和人工智能技术引入组合夹具设计中，可以提高生产效率、减轻劳动强度、缩短生产准备周期和加快产品上市时间。介绍了组合夹具计算机辅助设计的发展情况和研制的智能型组合夹具计算机辅助组装系统的结构及其功能，重点对系统中的智能模块做了阐述。     

CAFD中的夹具快速装配技术研究

近年来CIMS中的CAD、CAPP、CAM技术得到了长足的进展 ,然而基于CAD模型的夹具自动设计的研究还相对薄弱 ,尤其是夹具的自动装配技术。本文引入了有效表面和有效路径的概念 ,建立了快速装配模型 ,给出了功能结构及详细的夹具装配算法流程 ,为组合夹具的快速装配提供了一种切实可行的方法     

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.     

基于多层实例库的组合夹具辅助装配研究

针对计算机辅助夹具设计系统的功能需求,提出了一种组合夹具智能辅助设计的装配模型,建立了基于装配特征的元件库、以典型路径形式存储的典型组件库和包含夹持面域关系信息的典型结构库所构成的多层夹具实例库。采用了分层匹配的方式检索夹具结构、组件和元件,以完成夹具结构的装配过程,提出了一种自顶向下分层匹配的组合夹具智能辅助装配方法。     

基于虚拟现实的组合夹具组装系统研究

针对计算机辅助组合夹具设计存在的问题,提出了一个基于虚拟现实的组合夹具组装系统。给出了系统的功能模型和体系结构,研究了组合夹具虚拟装配模型、虚拟环境下组合夹具元件的装配定位等关键技术和解决方案。提出了基于多视图的组合夹具虚拟装配模型,该模型便于信息表达和管理,符合虚拟环境的表达和组织原则,解决了元件重复使用问题。提出了基于模糊评判的几何约束自动识别方法,对待装配件与装配基准件的装配特征进行匹配和优化选择,实现装配操作意图的准确捕捉。应用实例表明,原型系统能够很好地支持组合夹具组装设计。     

三维组合夹具数据库设计及装配技术研究

为了改变组合夹具传统的实物试装模式,提高组合夹具设计的效率和质量,从实用性和易用性的角度出发,以UG为平台,建立组合夹具的三维数据库和组装系统。利用该系统,夹具设计师可在计算机中快速模拟组装组合夹具,以完成夹具的三维设计并生成二维工程图纸,以此指导夹具的实际组装。     

基于网络的夹具设计信息模型与应用研究

根据夹具设计特点论述了集成工艺设计中夹具设计信息数据结构，应用面向对象的方法描述了夹具设计的制造工艺信息类和制造资源信息类体系结构，建立了数据结构中夹具设计的装夹工艺模型和夹具资源模型，根据建立的信息模型开发了装夹工艺信息子系统和夹具资源信息子系统，并在网络环境下得到了应用。     

组合夹具结构设计自动化系统研究

在广义映射原理指导下,开发了支持“top-down”风范的组合夹具设计自动化软件系统。在对零件夹持特性分析基础上,提取夹具需求信息,建立了组合夹具的功能要求集合,并对组合夹具功－构映射关系进行了全面分析,对组合夹具概念结构实施多方案重构,并进行了实例验证。为夹具结构设计自动化软件系统的开发探索出一条新的途径。     

组合夹具装配虚拟设计

介绍了一个基于ＰＣ的组合夹具虚拟装置设计系统（ＶＤＭＦＳ）的开发过程,并分析探讨了该方法的不足及以后开发的方向。     

槽系组合夹具计算机辅助拼装系统的研究

从目前中国生产和使用的组合夹具大多是槽系组合夹具的现状出发,制定了槽系组合夹具计算机辅助拼装系统的实施方案并编制了软件.论述了构成系统的各主要模块的功能、系统的工作流程以及实现组合夹具计算机辅助拼装系统实用化、商品化所需要解决的主要技术问题.     

具有特征信息的三维孔系组合夹具元件库的建立

从组合夹具元件的功能出发，分析了夹具元件特征的具体定义，构成及分类；讨论了具有特征信息的三维孔系组合夹具元件库的建立方法；介绍了用ARX技术实现特征信息检索的关键程序，支持了夹具自动设计系统。     

PDM/CAFD集成技术研究

PDM作为 CAD/CAPP/CAM的集成平台越来越受到人们的重视 ,但其对计算机辅助夹具设计 (CAFD)的支持却很少有人关注。本文在分析了基于 PDM的集成化夹具设计系统体系结构后 ,着重研究了基于 PDM的组合夹具设计模型构建技术 ,并在此模型基础上实现夹具的快速设计和装配 ,以有效地支持并行工程的实施。     

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.