A systematic conceptual design of modular fixtures

The replacement of dedicated fixtures by modular fixturing systems seems to be a trend in the manufacturing field, especially in meeting the desire for greater flexibility but the selection of appropriate modules from a modular fixturing system and subsequent assembly is itself not an easy task. This research provides a systematic design method to help dedicated fixture users to convert to modular fixturing system users. This method classifies modules into five functional groups and then selects proper modules from each group in accordance with the functional request of the fixture assembly. This systematic design of modular fixtures helps a dedicated fixture user to build an economical and efficient modular fixturing 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.     

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.     

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).     

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.     

Weld Pattern Design for Sheet Metal Laser Welding Considering Fixturing Quality

In sheet metal assembly by laser welding, metal fit-up is an important specification for achieving welding quality. The fixture plays an important role in satisfying the intimate metal fit-up that laser weld requires. The fixturing quality for sheet metal laser welding is directly related to the assembly weld patterns used (weld location, weld length, etc.). The design of assembly weld patterns is a critical phase in the fixture design cycle. Traditionally, the determination of the weld pattern is based on the designer’s experience. Because of this it is quite easy to cause unexpected deviations from the assembly weld quality requirements. In this study, a new computer-aided design approach for the assembly weld pattern is developed, where the sources of variation in the weld areas of the parts are considered in detail. Using this approach, the weld location and the weld length obtained are much more reasonable and cost-justified. A simple example and a case study show that the approach presented for assembly weld pattern design can reasonably meet the fixturing quality requirements.     

Reconfigurable modular automation systems for automotive power-train manufacture

This paper describes research towards the realization of reconfigurable modular automated machines and the associated engineering methods and tools necessary to support their lifecycle needs. UK-based research, in collaboration with the Ford Motor Company and several machine builders, has resulted in the development of full-scale prototype reconfigurable modular automation systems for both engine assembly and machining applications. The implementation of an assembly system is featured in this paper. An engineering environment and associated reconfigurable component-based control system architecture have been created aimed at supporting the lifecycle needs of a new generation of agile automated systems, i.e., providing reconfigurable, easily scalable automated machinery. This approach has the potential to fit within a wider collaborative automation strategy where manufacturing systems are implemented as a conglomerate of distributed, autonomous, and reusable units.     

自动化装配设备的总体设计

根据自动化装配设备的特点,提出在自动化非标装配设备设计中,从装配工艺、功能分析、结构布局、机构系统和控制系统等方面进行总体设计,优化和合理的总体设计可以加快非标装配设备的设计进度,保证自动化装配设备系统的可靠性.     

基于线性不等式方程组解的存在性及其通解的工件可达/可离性分析算法

工件的可达/可离性反映了将工件安装到/脱离出夹具装夹布局的可能性,分析可达/可离性有助于在工件上正确选择装夹表面和装夹点。为此依据工件与装夹元件的实际接触或装配情况,利用泰勒定理提出了工件可达/可离性模型。通过将工件安装到/脱离出装夹布局的可能性等价于可达/可离性模型的解的存在性,借助任意数可表达为两个非负数之差这一数学技巧作为桥梁,将工件可达/可离性模型的解的存在性问题转化为线性规划问题,提出了工件可达/可离性的判断方法。尤其是在判断可达/可离性模型有解的情况下,继而考虑了工件安装到/脱离出装夹布局的方向性。在此基础上,进一步将可达/可离的方向性转化为可达/可离性模型的通解,由此构建了求解线性不等式方程组的Γ-算法。这个“先有解-再求解”的算法仅涉及到装夹元件在工件表面处的位置与单位法矢量信息,不仅适用于形状复杂的工件,而且避免了可达/可离性模型无解情况下依旧求解的局限性,同时也拓展和丰富了自动化夹具设计的理论基础。     

Quality design of fixture planning for sheet metal assembly

Fixturing plays an important role in enhancing weld quality of the sheet metal assembly process. However, traditional experience-based fixturing schemes and purely optimal fixturing schemes are often sensitive to location fluctuation of the designed locators. In this paper a mathematical representation of deterministic locating and total fixturing for a flexible workpiece is developed first, then a virtual beam model is proposed to evaluate the degree of flexibility of the locating points. A quality design model of fixture planning for sheet metal assembly with resistance spot welding is then developed; both the performance expectation and the variance are considered in the formulation of the objective function; a prescribed factor is used to weight the two objectives. The finite element model based on ANSYS software is set up with a spot weld feature employed and genetic algorithm is used in the optimization process. A simple example and an industrial case illustrate the feasibility of the developed model. This work provides a basis for improving the quality of sheet metal assembly in the design phase.     

岸边集装箱起重机金属结构数字化设计技术

研究了岸边集装箱起重机参数化设计和模块化设计的方法,采用产品参数化设计、主要部件自动装配、专家设计系统及识别记忆、多系统设计平台数据自动调用与共享、以及智能化模块集成与扩展等技术,开发了岸边集装箱起重机系列产品金属结构模块式参数化设计系统,采用完全程序化参数建模的方法,将参数化设计思想扩展到工程图,实现了工程图的自动调整,改变了传统的2D设计手段,大幅度提高了岸边集装箱起重机金属结构的设计效率与质量,缩短了新产品的开发周期,具备了快速响应个性化的市场要求的能力。     

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.     

Representation of similarity and dependency for assembly modularity

Researchers have expanded the definition of product modularity from function-based modularity to life-cycle process-based modularity, and developed a measure of product modularity and validated a corresponding modular product design method. However, a correct modularity measure and modular design method are not enough to realize modular product design. How the measure and design method are used, especially the role of product representation, is an important aspect of modular design and imperative for realizing the promised cost savings of modularity. In this paper, we develop a representation that includes similarity and dependency for assembly modularity. The similarity representation is based on assembly cost factors including tool changes and fixture changes. The process-based design dependency representation is based on design features that impact the assembly process (faces, fasteners, assembly interference, etc.). This representation captures the cost benefits of modularity and can be extended to other life-cycle processes. A set of products is used to show the application of this representation in association with a modularity measure and modular design method.     

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。     

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。     

轿车车体装配偏差研究方法综述

本文从轿车车体焊接、工夹和装配制造全过程出发,概述了轿车车体装配偏差研究方法和研究现状,详细讨论了车体柔性薄板件装配偏差研究的理论模型及车体装配偏差的监测与统计技术,最后提出了面向全生命周期的车体制造装配偏差设计与评价思想。     

通用液压渗漏测试系统的设计

该文主要论述了一种检测液压产品及系统渗漏的通用方法,并对其测试的原理予以分析。该设计的原理具有通用性好,易于模块化设计,又因其成本易于控制,既可应用于低成本的手动测试装置,又可通过增加控制单元,构成高效自动化的测试平台。     

A model for measuring complexity of automated and hybrid assembly systems

The demand for delivering product variety has been increasing. Increased product variety caused by product customization, personalization, evolution and changes in their manufacturing systems. Variety allows manufacturers to satisfy a wide range of customer requirements, but it can also be a major contributing factor to increased complexity of assembly. Complexity is generally believed to be one of the main causes of the present challenges in manufacturing systems such as lengthy and costly design processes, higher life cycle costs and the existence of numerous failure modes. Complex assembly systems are costly to implement, run, control and maintain. Assessing complexity of assembly helps guides designers in creating assembly-oriented product designs and following steps to reduce and manage sources of assembly complexity. On the other hand, reducing complexity of assembly helps lower assembly cost and time, improves productivity and quality and increases profitability and competitiveness. The complexity of assembly should be assessed by considering both products and their assembly systems. In this paper, a structural classification coding scheme has been used to measure assembly systems complexity. It considers the inherent structural complexity of typical assembly equipment. The derived assembly systems complexity accounts for the number, diversity and information content within each class of the assembly system modules. A domestic appliance drive assembly system is used to demonstrate the use of the classification code to calculate the assembly system complexity. The developed complexity metrics can be used by designers as decision support tools to compare and rationalize various automated assembly systems alternatives and select the design that meets the requirements while reducing potential assembly complexity and associated cost.