Optimization of Fixture Number in Large Thin-Walled Parts Assembly Based on IPSO

There are lots of researches on fixture layout optimization for large thin-walled parts.Current researches focus on the positioning problem,i.e.,optimizing the positions of a constant number of fixtures.However,how to determine the number of fixtures is ignored.In most cases,the number of fixtures located on large thin-walled parts is determined based on engineering experience,which leads to huge fixture number and extra waste.Therefore,this paper constructs an optimization model to minimize the number of fixtures.The constraints are set in the optimization model to ensure that the part deformation is within the surface profile tolerance.In addition,the assembly gap between two parts is also controlled.To conduct the optimization,this paper develops an improved particle swarm optimization(IPSO)algorithm by integrating the shrinkage factor and adaptive inertia weight.In the algorithm,particles are encoded according to the fixture position.Each dimension of the particle is assigned to a sub-region by constraining the optional position range of each fixture to improve the optimization efficiency.Finally,a case study on ship curved panel assembly is provided to prove that our method can optimize the number of fixtures while meeting the assembly quality requirements.This research proposes a method to optimize the number of fixtures,which can reduce the number of fixtures and achieve deformation control at the same time.

Development of Fixture Layout Optimization for Thin-Walled Parts:A Review

An increasing number of researchers have researched fixture layout optimization for thin-walled part assembly during the past decades.However,few papers systematically review these researches.By analyzing existing literature,this paper summarizes the process of fixture layout optimization and the methods applied.The process of optimization is made up of optimization objective setting,assembly variation/deformation modeling,and fixture layout optimization.This paper makes a review of the fixture layout for thin-walled parts according to these three steps.First,two different kinds of optimization objectives are introduced.Researchers usually consider in-plane variations or out-of-plane deformations when designing objectives.Then,modeling methods for assembly variation and deformation are divided into two categories:Mechanism-based and data-based methods.Several common methods are discussed respectively.After that,optimization algorithms are reviewed systematically.There are two kinds of optimization algorithms:Traditional nonlinear programming and heuristic algorithms.Finally,discussions on the current situation are provided.The research direction of fixture layout optimization in the future is discussed from three aspects:Objective setting,improving modeling accuracy and optimization algorithms.Also,a new research point for fixture layout optimization is discussed.This paper systematically reviews the research on fixture layout optimization for thin-walled parts,and provides a reference for future research in this field.

Design a Special Fixture for Tractor Lever

Aiming at the problems of long time and poor machining precision in processing the tractor lever workpiece,a special fixture suitable for the tractor lever workpiece is designed by analyzing the processing technology of the lever workpiece,and the workpiece is accurately positioned and tightened under the action of the special fixture.Efficient machining of the workpiece can be achieved by using a drill template.The fixture not only has the advantages of high production efficiency,low cost and high life,but also effectively improves the processing technology of the workpiece,and has certain reference value for the subsequent fixture improvement design.

Flexible Fixture Design for the Top and End Surface Processing of NP2_NP4 Cylinder Heads

This paper focuses on the design of fixtures for NP2 and NP4 cylinder heads on a horizontal machining center of flexible machining automatic lines.It began with an analysis of the diagrams of part processing and working procedure which formed the basis for the design of the processing technology scheme,a selection of suitable machine tools,and the setting of processing parameters.Fixtures tailored to the chosen machine tools were then designed to meet the processing requirements.Additional aspects of the project included the design of part drawings,calculation of working time quota,design of auxiliary guides,support clamping,and hydraulic circuits,all aimed at fulfilling practical production requirements.

THE RESEARCH OF MANUFACTURING TOOLS(FIXTURES) PLANNING FOR ARMOURED FLEXIBLE CONVEYOR (AFC) USING CAD TECHNIQUE

The deepth and width of CAD application in coal mining equipments need promote furtherly. The information stream method is applied as the main clue to deal with the related technology and problems in research of manufacturing tools (Fixtures) planning for AFC (mining scraper bars conveyor) using CAD technique.

精密薄壁轴套柔性检验方法及工序能力评价

航空航天零件要求精度高,合格率要达到100%,常采用三坐标测量来提高测量精度,减少人员测量带来的误差。精密薄壁轴套零件作为连接元件在工作中起到轴向定位和径向紧固的作用,对机械传动起着重要的作用。为保证零件的测量精度和合格率,需要将测量产生的工艺误差控制在零件公差的1/3以内,工艺误差包含定位误差、夹紧变形误差等。试验利用光固化柔性夹具对轴套进行夹紧,减少金属夹具对轴套产生的变形和损伤,消除夹紧变形误差。利用对同一个轴套零件进行重复测量,获得定位误差引起的标准不确定度,并结合工序能力计算,来判定测量方法的可行性。

基于低频悬吊系统的安装灯具斜拉索驰振性能风洞试验研究

灯具会改变斜拉索的气动外形,可能诱发驰振现象。为研究不同灯具对斜拉索驰振性能的影响,以某大跨斜拉桥斜拉索为研究背景,开发了一种节段模型低频悬吊系统,开展了节段模型测振风洞试验,研究了0°~180°风攻角条件下安装抱箍式、贴合式和分离式三种灯具斜拉索的驰振性能,并分析了附加阻尼对安装灯具斜拉索驰振临界风速的影响。研究结果表明:灯具类型和斜拉索直径是影响斜拉索驰振性能的重要因素。安装抱箍式灯具斜拉索未发生驰振现象,而安装贴合式灯具斜拉索和分离式灯具斜拉索均在低风速下发生了驰振,说明贴合式灯具和分离式灯具会降低斜拉索的驰振稳定性。安装贴合式灯具时,直径200 mm斜拉索的不利风攻角是160°,而直径260 mm斜拉索的不利风攻角是30°和150°;安装分离式灯具时,直径200 mm斜拉索的不利风攻角是20°,而直径260 mm斜拉索未观测到驰振现象。增大阻尼能提高斜拉索的驰振临界风速。相关研究成果可为安装灯具斜拉索的驰振性能及减振控制研究提供重要参考。

CNC SYSTEM OF FLEXIBLE FIXTURE IN AIRCRAFT COMPONENT MANUFACTURING AND ASSEMBLY

The computer numerical control（CNC） system is suited to control varied types of flexible fixtures in aircraft component manufacturing and assembly. The mechanisms and control requirements of flexible fixtures are presented and analyzed. The hardware and software architecture and implementation of CNC system are pro- posed. The flexible fixture mechanism is described using configuration parameters. According to the parameters, the CNC system automatically generates the control feature and the human machine interface （HMI） operation function. The CNC system is implemented in a flexible fixture for skin-strlnger assembly, and results show the effectiveness of the system.

河北省丝孢菌研究 Ⅲ、漆斑菌属(Myrothecium Tode:Fr.)的四个种

本文报道了寄生或腐生于植物上的漆斑菌属(Myrothecium Tode: Fr.)真菌4个种。其中白毛漆斑菌(M. leueotrichum(Peck)Tulloch)为中国新记录种;另外还报道了露湿漆斑菌(M. roridum Tode: Fr.)的几种新寄主植物。文中有种的鉴定特征描述和分种检索表。

新质生产力背景下的“智能夹具开发与调试”课程改革与实践

对新质生产力背景下“智能夹具开发与调试”课程的改革与实践进行了研究,对生产力发展对课程内容和教学模式提出的新要求进行了探讨,介绍了课程改革的实施策略,包括教学内容的优化与更新、实践教学环节的强化以及多元化教学模式的探索,总结了学生实践能力的提升以及教师反馈与教学反思的经验。旨在为智能制造相关课程的教育改革提供借鉴和参考。

基于通道注意力的多任务卡具缺损检测算法

为及时地发现铁路通信漏缆卡具缺损现象,保障铁路运营安全,该文提出一种基于通道注意力的多任务卡具缺损检测算法。在YOLOv7-tiny的基础上,该算法通过在检测头增加通道注意力机制的方式,平衡不同通道之间的重要程度,提高了模型检测能力。为了实现对卡具的状态检测,算法在类别损失函数中额外增加一项状态损失,并在其中嵌入Focal loss来克服样本不足的问题。为了验证算法的有效性,该文分别对实际线路中的四种类型卡具进行实验。实验结果表明,该文提出的算法效果好、速度快,能满足实际现场需求。

一种防雷检测气动检测夹具的研发

现代的楼宇建筑由于外观造型效果和安全要求,屋面上很多情况下已不设置人员登高处,这就导致了技术人员已无法去到现场对接闪器的情况进行检查。接闪器在防直击雷装置中扮演着十分重要的角色,它与大地连通与否直接关系到所保护的建(构)筑物是否能够得到足够的保护。本文介绍了采用具有悬停功能的大负载系留式无人机为平台,挂载一套气动夹具和打磨除锈工具的检测装置送至高处接闪器,对其进行接地电阻检测。

Modeling and Compensation Technology for the Comprehensive Errors of Fixture System

Error modelling and compensating technology is an effective method to improve the processing precision.The position and orientation deviation of workpiece is caused by the fixing and manufacturing errors of the fixture.How to reduce the position and orientation deviation of workpiece has become a technical problem of improving the processing quality of workpiece.In order to increase machining accuracy,an implementation scheme of fixture system comprehensive errors（FSCE） compensation is proposed.A FSCE parameter model is established by analyzing the influence of contact points on the position and orientation of workpiece.Meanwhile,a parameter identification method for FSCE parameter model is presented by using the 3-2-1 deterministic positioning fixture,which determines the model parameters.Moreover,a FSCE compensation model is formulated to study the compensation value of the cutting position.By using RenishawOMP60 Probe and combining vertical machining centre（SKVH850） equipment with SKY2001 Open CNC System,on-machine verification system（OMVS） is built to measure FSCE successfully.The processing error can be reduced by analyzing the cutting position of the tool with the homogeneous transformation of space coordinate system.Finally,the compensation experiment of real time errors is conducted,and the cylindricality and perpendicularity errors of hole surface are reduced by 30.77% and 28.57%,respectively.This paper provides a new way of realizing the compensation of FCSE,which can improve the machining accuracy of workpiece largely.

伺服机构冲击故障分析与改进

针对伺服作动器在进行力学环境试验(振动、冲击)后,产品性能复测时出现异常抖动,分解发现安装于作动器滚珠丝杠副处的导向轴承发生断裂,该问题影响产品可靠性。借助理论结合有限元仿真进行失效机理分析表明:作动器与试验夹具安装连接处存在间隙,致使导向轴承在试验中实际响应量级被放大,径向承受过大载荷导致轴承发生断裂。依据分析结果,对试验夹具进行优化设计,并顺利通过振动、冲击试验考核。方法对设计此类作动器进行力学环境试验,以及对产品实际激励响应分析具有一定的工程指导意义。

LOCATORS OPTIMIZATION FOR MEASURING FIXTURE DESIGN

'N-2-1' principle is widely recognized in the fixture design for deformablesheet metal workpieces, where N, the locators on primary datum, is the key to sheet metal fixturedesign. However, little research is done on how to determine the positions and the number of Nlocators. In practice, the N locators are frequently designed from experience, which is oftenunsatisfactory for achieving the precision requirement in fixture design. A new method to lay outthe N locators for measuring fixture of deformable sheet metal workpiece is presented, given thefixed number of A'. Finite-element method is used to model and analysis the deformation of differentlocator layouts. A knowledge based genetic algorithm (KBGA) is applied to identify the optimumlocator layout for measuring fixture design. An example of a door outer is used to verify theoptimization approach.

FLEXIBLE ASSEMBLY FIXTURING LAYOUT MODELING AND OPTIMIZATION BASED ON GENETIC ALGORITHM

There are many welding fixture layout design problems of flexible parts inbody-in-white assembly process, which directly cause body assemble variation. The fixture layoutdesign quality is mainly influenced by the position and quantity of fixture locators and clamps. Ageneral analysis model of flexible assembles deformation caused by fixture is set up based on'N-2-l' locating principle, in which the locator and damper are treated as the same fixture layoutelements. An analysis model for the flexible part deformation in fixturing is set up in order toobtain the optimization object function and constraints accordingly. The final fixture elementlayout could be obtained through global optimal research by using improved genetic algorithm, whicheffectively decreases fixture elements layout influence on flexible assembles deformation.

A Study on Modular Fixture Design with Intelligent Selection of Elements and Interactive Assembly

Based on the features of the design and assembly of rnodular fixtures, a new design system which combines intelligent selection of elements and interactive assembly is presented.Using the fixture design datum, the system can automatically select elements,and can interactively assemble together these elements based on AutoCAD. An example is given to illustrate it.

Numerical simulation of horizontal transversal displacement under different fixed clamping force of welding fixture for superalloy during TIG welding

A numerical model is established by Abaqus software for superalloy during tungsten inert gas （TIG） welding with welding fixture to simulate the weld temperature filed, stress and strain field, and weld plate＇s horizontal trasnsveral shift. The clamp force perpendicular to the weld plate varying with welding time was analyzed. The maximum clamp force during welding process was calculated. Under the condition of insufficient of clamping force, a half or one third of the maximum clamp force for example, the weld plate＇s horizontal transversal displacement could happen and also be computed.

Parametric Design of Modular Fixture Structure

Based on an example of its typical structure, the concept of modular fixture structure module is presented, and the structure module system of modular fixture is summarized. Then the parametric design of structure is discussed, and its advantages are also emphasized.Furthermore, some specific methods are provided, such as the selection of fixture components, the determination and input of parameters, drawing representative model,and the creation of drawing. Finally an applied example of strcture parametric design is presented.

Application and Realization of Rapid Searching Technology in the RL & SM Universal Fixture System

A searching-machining system of RL & SM (Rapid Location and State Memory) universal fixture is here introduced, and the concept of rapid searching technology and manufacturing information transformation is then described, with the appropriate control methods and key techniques for its realization being proposed and also practically realized. Theoretical analysis and experimental results show that the proposed idea and methods are feasible to serve as in the practical application of the RL & SM system.