定位夹紧块夹具在T型导轨面上的应用

在机械加工设备中的T型槽工作台上,设计了专用定位夹紧块夹具。其原理是利用夹紧块间的摩擦力,转变成夹紧力,定位夹紧工件。该夹具结构简单,使用灵活方便,特别能够解决大中型工件平面的一次性粗、精加工。     

薄壁套类零件的车削夹具

针对薄壁套类零件的加工,设计了如图所示的夹具,该夹具利用夹具体2上的刚性部分对工件进行精确定位.夹紧时,拉杆1左移,通过螺母7、平垫6和隔套5促使橡胶圈4挤压变形将工件1夹紧,利用橡胶压紧后产生的摩擦力来传递扭矩,由于橡胶对钢的摩擦系数是钢对钢的摩擦系数的8倍,因此只须用原来l/8的夹紧力即可实现可靠夹紧,同时由于橡胶材料塑性好,不易使工件发生变形.松开时,拉杆1右移,橡胶圈4恢复原状,夹紧力消除,即可取下工件.     

胀条式自动定心夹具

我厂在加工干式铸铁气缸套生产线上,有一道工序是平两端面及车定位圆,加工设备选用为C7620液压车床,夹具是胀瓣式自动定心夹具。胀瓣合在一起为圆形,加工时经常产生夹具旋转,而工件不转,使刀具损坏严重。分析其原因,主要是夹具的外胀圆瓣与缸套内孔接触不良,摩擦力小引起。为此我们设计了胀条式自动定心夹具,解决了这一问题。     

一种高效率汽车调整臂壳体夹具的设计与分析

为提高汽车调整臂壳体工件的加工精度与效率,针对铣削前后两平行端面工序,提出一种快速装夹铣削夹具。该夹具能够利用卧式铣床一次走刀完成两个工件的该工序加工,大幅度提高生产效率。通过剖析夹具的整体结构和夹紧力计算,运用有限元分析法确定夹具的易损位置,指导夹具后期维护。对调整臂壳体工件进行模态分析与变形分析,避免加工共振并确保夹具满足加工精度要求。该夹具大幅缩短加工时间,提高加工精度与稳定性,取得了良好的实际应用效果。     

智能滚齿机刀具、夹具及工件识别与匹配系统的设计

为解决智能滚齿加工中刀具、夹具及工件的误用问题,提出了一种刀具、夹具及工件与任务配套检验的方法,并基于该方法设计了智能滚齿机刀具、夹具及工件识别与匹配系统(IMS-CFW)的总体架构。对系统功能实现中涉及到的识别技术进行了研究,包括激光标刻二维条码识别技术和无线射频识别(RFID)技术相结合的刀具、夹具及工件识别方法和针对在机识别时存在的加工干涉和易碰撞等问题,提出了基于模糊自整定PID算法的夹具RFID读写头移动定位控制方法和基于RFID设备读取时间的刀杆轴和夹具轴的转动控制方法。最后,开发了识别与匹配系统,并通过案例验证了该系统能有效缩短加工准备时间和解决刀具、夹具及工件的误用问题,从而提高生产效率和加工质量,具有实际推广价值。     

某盘型工件内外自由曲面自动化测量夹具设计

针对某盘型工件的内外自由曲面测量需人工参与装夹、自动化程度低的问题,通过分析该工件的检测工艺和特点,沿用原有检测工装的定位固定思路,针对性地设计了一款专用自动化检测夹具。对该自动化夹具进行实际功能验证,证明该夹具能满足盘型工件内外自由曲面一次装夹同时测量的功能需求。此外,通过将该夹具与机械臂、坐标测量机相结合,可实现盘型工件的自动上下料及检测,有效提升该工件检测的自动化程度和检测效率。     

伸缩式对称夹具的设计

伸缩式对称夹具可以夹持不同类型不同厚度的工件,工件的厚度变化不会影响工件固定后的中心线。并且该夹具的夹持头可以缩回夹具架,该夹具还具有安装空间小,夹持力大等优点。     

基于改进MOEAD算法的零件加工布局优化研究

在机械加工中,夹具布局优化本身是一个多目标优化问题,目前夹具布局优化大多是以工件位置总位移最小为目标函数,视作单目标优化问题处理.针对这种情况,提出一种改进的多目标进化算法.该方法以x,y,z三个方向上的偏移量作为目标函数,引入基于高斯变异的迁移行为对基于分解的多目标进化算法(MOEAD)进行改进,满足了夹具布局中的定位点有大量的组合方式,对算法拥有较强搜索能力的需要.通过测试函数和铣通槽的实例分析,验证了该方法拥有更强的搜索能力和揭示了工件在各方向上偏移量之间的相互关系,为获得更合理的布局提供了参考依据.     

一种模块化真空吸附式组合夹具的研制与应用

介绍了一种通用程度高的模块化真空吸附组合夹具的研制与应用,重点说明了夹具模块的结构、相关技术参数的分析与确定。该夹具结构简单、适应性强,通过夹具模块的组合可用于各种不同尺寸的薄壁工件的装夹,且装夹可靠并能保证工件的加工质量。     

基于矢量角度和优化技术的定位误差新算法

在夹具设计中,为了分析与计算定位误差,保证工件的加工精度,提出了基于矢量角度和优化技术的定位误差自动算法.首先通过工件与央具的装配结构关系,建立了经过接触点的定位误差尺寸链搜索方法;然后基于矢量角度的推算,将定位误差尺寸链转化为有约束优化问题,以实现定位误差的自动计算.该方法为计算机辅助夹具设计系统的开发提供了基础理论.     

轴承磨削加工工装的研究与应用

电磁无心夹具广泛应用于轴承套圈磨削加工中。本文通过对电磁无心夹具工作机理的研究,针对传统的夹具调整方法调整周期长、精度差的现状,提出一种确定工件偏心量和偏心调整方向的新的工艺方法及其工装。研究发现,可以通过制做与被加工工件工况相同的标准偏心件,用该标准件直接调整夹具来代替传统的方法。这样可以大大缩短调整时间,提高调整精度,从而提高工序生产效率。     

IDEF0 Model of the Measurement Planning for a Workpiece Machined by a Machining Centre

A comprehensive analysis of the entire measuring operation for a workpiece machined by a machining centre should be conducted systematically before the application of a planning technique. For this purpose, an IDEF0 model is used in this paper to plan the measuring sequence and operation of a coordinate measuring system for a workpiece machined by a machining centre. Generally speaking, a machining centre can machine workpieces having complicated shapes. Therefore, the planning of measurement procedures and operations on a workpiece machined by a machine centre requires consideration of issues such as the position and measuring sequence of the measurement points, how to avoid probe collision during measuring, which fixture elements are required for measuring fixtures, and where the support points of fixtures and position of fixture locations should be.     

Effect of fixture compliance and cutting conditions on workpiece stability

This paper computes and investigates the effect of fixture compliance and cutting conditions on workpiece stability and uses it as a basis for selecting a suitable fixture among several alternatives. We use two criteria, the minimum eigenvalue of the fixture stiffness matrix and the largest displacement of the workpiece due to the cutting forces to assess the stability of the workpiece. First, the minimum eigenvalues of the fixture stiffness matrices, for the fixtures being considered, are computed. Second, since the eigenvalues are not dependant on the cutting forces, a displacement measure, the largest displacement of the workpiece due to the cutting force, is computed for each fixture. This displacement is a function of the cutting force and the fixture compliance. The choice of fixture is often a compromise between the two criteria. We also consider the combined influence of fixture compliance and cutting conditions on workpiece stability. The results from the simple study used for illustration show that the eigenvalues remain constant under different cutting conditions whilst the largest displacement reduces by 68%, a significant reduction.     

接触变形对工件加工误差的影响

基于工件的准静态受力分析 ,运用经典Hertz接触理论 ,计算夹具 工件接触区的变形。根据多刚体运动学 ,建立表面加工误差和接触变形的关系 ,对加工误差进行预报。此方法也可用来计算定位基准误差对加工误差的影响。     

变速箱输入轴滚矩形花键工装改进

由于现有夹具缺陷导致工件矩形花键经常发生滚偏现象,改进夹具结构,使得铁屑不会掉入夹具内,影响夹具夹紧工件,有效克服旧夹具的缺陷,降低生产线废损率,提高生产效率,实现精益化生产,为公司降低成本,增加市场竞争力。     

Numerical simulation of the system “fixture–workpiece” for lever machining

In this article, the new configuration of fixture was proposed for ensuring the sufficient tool accessibility, which allows carrying out multiaxis machining of levers in one setup. The research based on numerical simulation was confirmed that the proposed fixture corresponds to all the accuracy parameters. Workpieces from steel, cast iron and aluminium alloy were investigated within the simulation. The values of displacements and stresses occurring during machining are less for proposed fixture in comparison with the existing fixtures that was confirmed by the deflected mode analysis. The modal analysis proved that the proposed fixture has much higher value of eigenfrequency than the other fixtures. To optimize the machining, the dependences for displacements and stresses on the cutting depth were determined. Oscillations of the system “fixture–workpiece” during machining were investigated for various manufacturing steps of levers machining of the fixtures from different fixture systems. The results of harmonic analysis showed that the dynamic stiffness of the proposed fixture was higher than that for the dedicated and modular fixtures. The oscillation amplitudes in the places of machined surfaces in the proposed fixture do not exceed the tolerance requirements for lever manufacturing.     

Development of a finite element analysis tool for fixture design integrity verification and optimisation

Machining fixtures are used to locate and constrain a workpiece during a machining operation. To ensure that the workpiece is manufactured according to specified dimensions and tolerances, it must be appropriately located and clamped. Minimising workpiece and fixture tooling deflections due to clamping and cutting forces in machining is critical to machining accuracy. An ideal fixture design maximises locating accuracy and workpiece stability, while minimising displacements.The purpose of this research is to develop a method for modelling workpiece boundary conditions and applied loads during a machining process, analyse modular fixture tool contact area deformation and optimise support locations, using finite element analysis (FEA). The workpiece boundary conditions are defined by locators and clamps. The locators are placed in a 3-2-1 fixture configuration, constraining all degrees of freedom of the workpiece and are modelled using linear spring-gap elements. The clamps are modelled as point loads. The workpiece is loaded to model cutting forces during drilling and milling machining operations. Fixture design integrity is verified. ANSYS parametric design language code is used to develop an algorithm to automatically optimise fixture support and clamp locations, and clamping forces, to minimise workpiece deformation, subsequently increasing machining accuracy. By implementing FEA in a computer-aided-fixture-design environment, unnecessary and uneconomical “trial and error” experimentation on the shop floor is eliminated.     

Automated setup and fixture planning system for box-shaped parts

The topic of the research is related to the domain of computer-aided manufacturing process planning. This paper deals with the problem of setup and fixture planning for the machining of box-shaped parts on the horizontal machining centres. The setup and fixture planning involves the definition of setups, the setup sequence and conceptual design of fixtures for each setup. The central topic of this research is the automation of the conceptual design of fixtures. This topic is interconnected with the setup planning, and accordingly, the aim of the author has been the integrated handling of tasks of setup and fixture planning and the finding of solution in an integrated system. Based on the workpiece model, the developed system automatically determines the setup sequence, the content of setups and the conceptual solution of fixture for each setup. The paper presents the problems of fixture solutions and the partial tasks of workpiece holding, the typical solution of partial tasks and the conditions of their application and finally offers a new method, which makes the integrated handling of tasks of setup and fixture planning and finding solution in an integrated system possible.     

A skeleton-retrieving technique for aiding modular-fixtures design

This paper presents a computer-aided approach to the design of modular fixtures by retrieving similar workpieces from an existing database. A database which stores previously-manufactured workpieces and their modular fixtures is assumed to be available. Each workpiece in the database is described by its skeleton and its boundary representation (BREP). The skeleton is a tree structure that describes the interior framework of a workpiece. Workpieces that have similar skeletons usually require similar fixturing configurations. For a new workpiece which requires a fixture to be designed, we first determine its skeleton and then retrieve existing workpieces with similar skeletons. The modular fixtures of these retrieved workpieces are displayed to assist engineers in designing new fixtures.     

Design and optimization of machining fixture layout using ANN and DOE

In machining fixtures, minimizing workpiece deformation due to clamping and cutting forces is essential to maintain the machining accuracy. This can be achieved by selecting the optimal location of fixturing elements such as locators and clamps. Many researches in the past decades described more efficient algorithms for fixture layout optimization. In this paper, artificial neural networks (ANN)-based algorithm with design of experiments (DOE) is proposed to design an optimum fixture layout in order to reduce the maximum elastic deformation of the workpiece caused by the clamping and machining forces acting on the workpiece while machining. Finite element method (FEM) is used to find out the maximum deformation of the workpiece for various fixture layouts. ANN is used as an optimization tool to find the optimal location of the locators and clamps. To train the ANN, sufficient sets of input and output are fed to the ANN system. The input includes the position of the locators and clamps. The output includes the maximum deformation of the workpiece for the corresponding fixture layout under the machining condition. In the testing phase, the ANN results are compared with the FEM results. After the testing process, the trained ANN is used to predict the maximum deformation for the possible fixture layouts. DOE is introduced as another optimization tool to find the solution region for all design variables to minimum deformation of the work piece. The maximum deformations of all possible fixture layouts within the solution region are predicted by ANN. Finally, the layout which shows the minimum deformation is selected as optimal fixture layout.