A novel approach to fixture layout optimization on maximizing dynamic machinability

In the aerospace industry, the reasonable layout of fixture can efficiently suppresses machining vibration of thin-walled aerospace structure during machining. Based on the analysis of typical structural components encountered in the aerospace industry, a general frame-structure workpiece with fixture constraints can be equivalent as Mindlin plates with simultaneous elastic edges and internal supports. On basis of the equivalent models, the powerful pb-2 Ritz method defined by the product of a two-dimensional polynomial and basic functions can be introduced to be taken as trial functions. Substituting displacement functions into energy functional and minimizing total energy by differentiation leads to eigenfrequency equations of the workpiece–fixture system. Consequently, a novel nonlinear programming problem based on the frequency sensitivity can be built to optimize the layout of fixture supports to maximize the fundamental nature frequency of the workpiece–fixture system. The feasibility of the proposed approach is validated by a machining case.     

A functional approach for the formalization of the fixture design process

The design of machining fixtures is a highly complex process that relies on designer experience and his/her implicit knowledge to achieve a good design. In order to facilitate its automation by the development of a knowledge-based application, the explicit definition of the fixture design process and the knowledge involved is a prior and a fundamental task to undertake. Additionally, a fundamental and well-known engineering principle should be considered: the functional requirements and their associated constraints should be the first input to any design process. Considering these two main ideas, this paper presents the development undertaken to facilitate the automation of the fixture design process based on a functional approach.In this context, the MOKA methodology has been used to elicit fixtures knowledge. IDEF0 and UML have been used to represent the fixture design process. A methodology based on the function concept and aiming to formalize such design process is proposed. Fixture functional requirements have been defined and formalized. Functional fixtures elements have been used to create a functional design solution, the link of these elements with the functional requirements and with typical commercial fixture components has been defined via tables and rules mapping. And finally, a prototype knowledge-based application has been developed in order to make an initial validation of the proposed methodology.     

计算机辅助组合夹具设计系统的研究与实现

组合夹具是解决小批量多品种、生产柔性化的有效手段,计算机辅助组合夹具设计是先进制造系统发展的必然要求.在现有夹具设计方法的基础上,建立计算机辅助组合夹具设计(CAMFD)系统的架构,并提出参数化的组合夹具元件建模技术以及基于粗糙集知识发现的组合夹具设计技术.并以槽系要素的组合夹具为实例证明了系统的实用性和有效性.     

Computer-Aided Group Fixture Design

A Computer-Aided Group Technology (G.T.) Fixture Design system (CAGFD) was developed based on the concept of fuzzy mathematics. The gradual character approach method was used to analyze common characteristics of similar parts and to assist the design of sophisticated G.T. fixtures. This paper addresses the issues of construction, functions and special characteristics of the proposed computer aided design system. Sample fixture design drawings for boring fixtures of bracket parts were provided as example.     

飞机薄壁零件装配偏差建模与仿真分析

为了准确有效地实现飞机薄壁零件装配偏差预测与控制,提出一种飞机薄壁零件装配偏差建模与仿真分析方法。根据飞机薄壁零件装配工艺过程,考虑零件制造偏差、工装夹具偏差和装配变形,基于确定性定位法和影响系数法建立装配偏差模型。在此基础上,基于蒙特卡洛法对装配偏差模型进行仿真求解,根据偏差源敏感度进行装配偏差优化。以某型飞机机身壁板装配偏差分析为例,验证了所提方法的有效性。     

通用薄壁类零件柔性夹具设计

薄壁类零件装夹及加工变形是夹具设计中需要重点考虑的问题。根据薄壁类零件的装夹特点,设计一种通用薄壁类零件柔性夹具,该夹具利用独特的径向支撑机构及对间隔环的灵活应用,可以实现对内径不同、长度各异的各种薄壁类零件的柔性装夹,有效克服薄壁零件在切削加工过程中的加工变形及装夹变形,从而保证零件加工质量的稳定性和生产效率的提高,且具有夹紧可靠、零件拆装方便、使用寿命长等特点。     

快装液压夹具的夹紧机理分析与维修

通过对夹具的结构和变形夹紧机理研究,分析了加压扭力和液体压力的关系,以及液体压力与弹性薄壁套的变形位移、弹性薄壁套受到的应力、对夹持棒的压力的关系。介绍了加压扭力的合理选取及夹具的装配方法。通过合理使用加压扭力和采用该装配方法,提高了夹具的使用寿命两倍以上,故障率仅为原来的30%。根据该机理自主研发的夹具能满足中等精度加工的需要,实现了进口夹具的国产化。     

基于SolidWorks的组合夹具CAD系统的开发

文章针对西安昆仑机械厂提出的数控机床用的组合夹具,常因生产时间交替,造成对同一零件,其组合夹具结构和安装方位差异较大,从而使编好的数控加工程序不能直接重复使用的问题,以SolidWorks为平台,建立了组合夹具CAD系统.该系统运用SolidWorks面向对象的参数化特征造型方法和成组技术原理,建立组合夹具元件库和对组合夹具进行分类、装配、管理.该系统的建立对组合夹具的推广,CAD/CAM的集成,有一定促进作用.同时,作者借助VC 6.0和SolidWorks的API函数对SolidWorks的二次开发进行了有益的探索.     

Optimisation of machining fixture layout under multi-constraints

Fixture layout including locator layout and clamp layout plays a vital role in fixture performance. Current researches have been focused on fixtures for components with regular geometry, the results of which are not always applicable for components with complex geometry. This paper presents a methodology of fixture layout optimisation carried out in consideration of the repeatability, immobility and stability of fixturing. The locator layout is optimised based on the criteria of workpiece repeatability and location accuracy. The clamp layout optimisation offers a method to minimize the magnitude of the clamping force. The procedure of clamp optimisation is (1) to find the feasible clamping position in terms of the immobility requirement; (2) to get the best clamp among the feasible clamping positions under constraint of the stability. The optimal fixture layout is considered in a global range and is especially suitable for the workpiece with complex surfaces. A fixture layout design for the aerofoil of a turbine blade is analysed as an example, and the optimal fixture layout is demonstrated.     

薄壁椭圆容器组焊夹具的应用

本文主要介绍薄壁椭圆容量的组焊夹具及其在我厂椭圆水箱上的应用。此组焊夹具的使用，为薄壁椭圆容器的批量生产，在质量和效率上提供了保证。这一组焊夹具对其它行业薄壁椭圆容器的生产，具有推广应用的价值。     

并联夹具机构灵巧性分析

针对汽车行业对制造系统以及包括夹具在内的所有部件的高模块化和灵活性的要求,提出一种具有高自配置性和灵活性的夹具系统。其中,安装在并联机构末端执行器上的夹具具有高刚度、高精度、可重构性,并且可以通过编程使其在工作空间中移动的特点。而并联机构作为自配置夹具系统的支持单元,在工作空间和动态特性方面具有一定的局限性。为了提高并联机构的综合工作性能,在工作空间中,分别以全局运动条件数和全局动态条件数作为运动灵巧性和动态灵巧性的评价标准。以工作空间体积、全局运动条件指标和全局动态条件指标为目标函数,对并联夹具机构进行优化,得到优化后的结构参数。     

大厚度比镍基高温合金构件的焊接工艺

基于Inconel718镍基高温合金材料的可焊性分析以及对大厚度比焊接件的结构分析,以1mm厚度的薄壁件为切入点研究了采用与不采用辅助夹具进行焊接定位的施焊效果。采用钨极脉冲氩弧焊方法使用辅助夹具对0.8mm厚度薄板进行焊接工艺试验,获得熔合良好的接头。大厚度比(1∶11)构件的焊接工艺应以控制热输入与防止薄壁件变形为原则,通过分析结构特点可利用夹具进行定位、辅助散热的作用制定出有效的焊接工艺。     

直吹管浇注料振动成型夹具的结构优化设计

针对直吹管浇注料振动成型夹具质量过大和动态特性差等问题,建立夹具优化数学模型,采用拓扑优化对夹具结构材料分布进行寻优,并在拓扑优化基础上以灵敏度分析筛选相关性较大的尺寸作为优化变量,基于Kriging法建立响应面模型,采用多目标遗传算法对振动夹具进行尺寸优化,两次优化后的夹具质量共减小了12.7%,1阶固有频率共提高了2.8%。对优化后夹具结构进行扫频振动响应仿真分析,验证了夹具优化设计的有效性及合理性,有效解决了直吹管浇注料振动成型夹具设计中容易出现的试验共振和夹具质量过大等问题。     

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 通过对高强度弹簧钢拉伸试验中钢材塑性结果失效原因的分析,阐述了试样加工的规范性以及试样夹具形状对拉伸试验结果的影响,提出由于拉伸试样与夹具之间不能保证同心,造成试验过程中产生偏载从而影响试验结果的真实性。依据保持试样与夹具同心这一原则针对性地提出了改进措施,采用楔形夹具夹持试样,通过试验取得了满意的结果。     

基于拓扑优化的薄壁零件装夹布局确定方法

在复杂薄壁件加工过程中,合理的定位点配置可以有效降低加工变形。为了解决薄壁件定位支撑结构的优化设计问题,文章建立了以刚度为目标函数,体积为约束函数的拓扑优化模型。模型将夹具与工件看作同一实体,采取多组件多约束的拓扑优化方法,利用大型商用软件Ansys Work-bench中的拓扑优化设计模块对零件的定位支撑结构进行拓扑优化设计,并对不同支撑条件的变形仿真结果进行了比较,证明了拓扑优化方法在夹具设计中应用的可行性。     

A model for synthesis of the fixturing configuration in pin-array type flexible machining fixtures

This paper presents a model for the synthesis of the fixturing configuration in pin-array type flexible machining fixtures. These fixtures possess an array of pins that hold parts by conforming to their shape. The proposed algorithm aims to achieve a specified level of fixture–workpiece conformability and stable equilibrium while keeping the workpiece rigid body motion due to fixture elastic deformation at or below a user-specified value. Specifically, the model finds the minimum clamping loads and the optimal number, position and dimensions of the pins necessary to achieve the conformability and stiffness goals for a workpiece having an arbitrary geometry and subjected to quasi-static machining/assembly forces. Experimental data for the X-clamp^® flexible pin-array vise is used to validate the proposed synthesis model.     

基于协作机器人的物流分拣软体夹具设计

为解决传统夹具适应性较弱的问题,设计一种以热塑性聚氨酯弹性体为材料的软体夹具。该材料低温柔顺性好、强度高,因此软体夹具可以与物体表面实现良好的贴合。利用SolidWorks完成软体夹具的方案设计,并在ABAQUS中进行夹爪适应性分析,计算夹爪抓取不同物体所产生的变形和应力。通过弯曲角度测试和末端接触力测试选择合适的夹爪长度,并通过3D打印制作软体夹具。在Baxter机器人上进行了质量测试和抓取试验,结果表明：该软体夹具可以有效、稳定、无损地抓取日常生活用品。     

组合夹具管理及辅助设计系统

夹具设计是生产准备过程的一个重要组成部分,组合夹具是FMS实现真正柔性的关键技术之一.组合夹具由于具有效率高、柔性好、可重复使用、成本低等优点而受到人们的重视.根据组合夹具的特点及某企业的实际需要,开发了组合夹具管理及辅助设计系统.系统包括组合夹具及其元件的库存管理,夹具设计信息录入、夹具检索、夹具组装、设计结果入库等夹具设计功能,定位误差计算和夹紧力计算等功能,建立了基于Pro/E的三维组合夹具元件图形库.最后介绍了系统的特点.     

一种工业机器人多功能夹具

针对目前工业机器人通用夹具可靠性低、夹持精度不高、生产效率低等问题,设计了一种多功能夹具,该夹具由两爪部分和三爪部分组成,可以实现平面类及轴类零件的装夹,并且拆卸简单、定位精度高,空间利用率高,能够保证工业机器人的工作效率。     

有效提升薄壁铝合金壳体零件数控铣削加工效率的工艺研究

针对一种薄壁矩形壳体零件难加工的特点,设计了一种薄壁矩形壳体零件数控铣削加工工装。通过该铣削工装的实际应用,结果表明:该工装的尺寸和形位公差都在要求规定的范围之内,保证了该类薄壁矩形壳体零件的加工质量与尺寸精度,减小了工件的变形量,简化了该加工工艺流程,极大地提高了生产效率。