大型薄壁件多点位自动化柔性支撑系统的位置优化研究

为解决多点位柔性工装系统在夹持大型薄壁件过程中需要满足定位形变量控制问题,基于“N-2-1”定位原理,针对均布算法局限,提出一种不依赖于外部操作者就能按照自生成原理实现系统的位置优化方法,并通过有限元软件Abaqus建立了大型薄壁件多点定位数值模型,采用先整体再局部依次进行位置优化。结果表明：优化后的支撑点位布局合理,系统资源利用率高,与单一整体位置优化相比,添加局部位置优化能够以最少支撑点位使得航空薄壁件更易达到工程要求;而对于局部存在缺陷无法进行支撑,则需考虑特定情况,调整相应支承机构点沿减小工件加工变形的最敏感方向移动,在局部变形较大的地方优化支撑点的数目,使得其变形相对于初始变形量显著下降,并且吸附压力也满足工程要求。     

新型机床夹具及其气控系统设计

1引言夹具是工件加工过程中，对工件进行夹紧的装置。夹具应满足以下使用要求：（1）在夹紧过程中应能保持工件的既定位置，更好地使工件得到定位。（2）夹紧应可靠和适当。既要使工件在加工过程中不产生移动和振动，同时又不使工件产生不允许的变形和表面损伤。（3）操作安全。方便、省力。本着上述使用要求，本文设计了桶盖自动央具。生产实践表明，该专用自动央具操作方便，安全可靠，自动化程度高。与原普通夹具相比，该自动夹具使桶盖生产效率提高了3惜。2夹具的设计（1）结构设计由于桶盖壁薄等特殊结构限制，使夹具的夹紧方式只能采…     

自动调节支承

图示为一种自动调节支承。它是用来给十字接头型工件或具有曲线表面的工件进行四点定位的。在壳体1的球面槽中装有球面支承,该支承制成两个对称部分2和3,它们能沿着结     

车管芯用的新式卡爪

介绍了一种车削管(环)类工件用的新式卡爪。该卡爪与普通卡盘配套使用。其最大的特点是：装夹时对薄壁管(环)不造成变形和损伤；工件只需一次装夹便可实现对其两个端面的切削加工；轻松快捷、安全可靠。管(环)类产品在批量生产过程中能提高生产效率和产品质量，降低加工成本及劳动强度，为自动化和半自动化专业生产提供了一种可实现的工件装夹方式。     

三爪定心卡盘在线切割机工件装夹中的应用

有一批如图1所示的零件，其中方形内孔的加工为该零件的最后一道工序。线切割机传统的支承夹具能提供1～2个定位面，工件依靠这些定位面进行装夹，但对这类零件采用该装夹方式并不恰当。考虑到该零件种类和数量较多，且外径尺寸变化较大，因而决定在线切割机上用三爪定心卡盘装夹工件进行加工。找几个精度较高的三爪定心卡盘并清洗干净，调整好线切割机工作台支架，然后把三爪卡盘固定在工作台支架上。紧固力要足够大，防止在装夹工件时卡盘移动而引起中心的变动。为了找出卡盘的定心中心，可制作一个内外圆同心度较高、粗糙度较低的试件夹…     

数控加工中心一次多件液压自动夹具设计

介绍一种用于汽车油管孔加工的多工件同时装夹的数控加工中心液压夹具。采用过定位解决了细长油管刚性差不便于装夹的问题,设计了夹具的机械结构和液压回路。一次多件同时装夹,高度自动的液压驱动,使得它是一种高效率自动夹具。     

薄壁套磨削夹具

在组合机床加工中,经常遇到各种固定套、导套之类的薄壁套加工问题。尤其是精磨时,常因装卡变形,造成工件成批报废,给工作带来很大困难。我们制造了一种简单磨内孔的夹具(见图),它只有4种零件组成,解决了装夹变形问题。夹具体1装夹在磨床卡盘上,定位预紧螺栓2只能作轻微定位用,不能起夹紧作用,调好后要用背帽固     

铁路货车端墙焊接机器人生产线

为铁路货车端墙配套的焊接机器人生产线,除了两套焊接机器人系统之外,设计制造了外围机械系统与电控系统。采用C型架上倒挂机器人与机器人行走相协调的控制方式,覆盖了端墙所需焊接的全部焊缝位置,获得了满意的焊接效果;所配套的工件自动传输机构、自动工件装夹定位机构及工件自动翻转机构,稳定可靠．最大限度地满足了端墙焊接生产的技术要求。     

转向架轴箱专用机床及夹具设计

对转向架轴箱的加工方案进行分析,设计钻孔专用机床。为了实现转架轴箱体一次装夹完成4-12 mm孔的加工,设计一套液压专用自动夹具。实践证明:该夹具结构简单,操作方便,加工过程中实现了对工件的快速定位装夹,提高了生产效率。     

基于PSO-BPNN和NSGA的薄壁件定位布局优化

为提高装夹布局优化计算的效率,同时考虑加工过程中振动对变形的影响,提出了融合改进的反向传播神经网络(back propagation neural network, BPNN)与快速非支配排序遗传算法(nondominated sorting genetic algorithms, NSGA-Ⅱ)的优化模型。首先,基于“N-2-1”定位原理,以定位点坐标为设计变量,薄壁件装夹变形和主振型位移为优化目标,通过有限元仿真建立了神经网络训练样本集;其次,引入粒子群算法(particle swarm optimization, PSO)改进神经网络,通过对有限样本集训练,构建了定位布局与装夹变形和振动位移之间的代理模型。实例结果表明,改进后的神经网络对装夹变形的预测精度提高了93%,对振动变形的预测最大误差仅为1.8%;最后,通过遗传算法求解预测模型得到了定位布局帕累托解集,进一步提高了优化效率。     

Flexible multibody dynamics based fixture-workpiece analysis model for fixturing stability

The machining force and torque exerted on a workpiece vary as the cutter moves along the tool path, therefore a dynamic approach is essential for fixturing stability analysis. This paper presents a technique to dynamically model and analyze the fixture-workpiece system subjected to time-varying machining loads. Combining the advantages of FEA (Finite Element Analysis) and nonlinear rigid body dynamics, a flexible multibody dynamic model is formulated to incorporate the overall interaction (clamping forces, machining loads, and contact friction) between flexible workpiece and compliant fixture elements. Three major parameters affecting the fixturing stability, namely the magnitude, application sequence, and placement of fixturing clamps, are analyzed. Additionally, the time dependent deformation of a flexible workpiece under clamping and machining loads is estimated. A scaled engine block with the 3–2–1 fixturing scheme subjected to face milling operation is given as an example. Comparison between the simulation result and experimental data shows a reasonable agreement.     

Improved workpiece location accuracy through fixture layout optimization

Inaccuracies in workpiece location lead to errors in position and orientation of a machined feature on the workpiece. The ability to accurately locate a workpiece in a machining fixture is strongly influenced by rigid body displacements of the workpiece caused by elastic deformation of loaded fixture–workpiece contacts. This paper presents a model for improving workpiece location accuracy in fixturing. A discrete elastic contact model is used to represent each fixture–workpiece contact. Reduction in workpiece locating error due to rigid body displacements is achieved through optimal placement of locators and clamps around the workpiece. The layout optimization model is also shown to improve the overall workpiece deflection and reaction force characteristics.     

基于夹具的工件自由度约束分析模型

夹具设计最主要的目的就是将工件精确定位.在定位过程中,工件自由度必须首先合理地受到约束以确定工件相对于刀具的正确位置.因此,分析工件的自由度约束情况是复杂定位方案设计甚至整个夹具设计的关键所在.本文基于刚体运动学,建立了分析工件自由度约束情况的定位原理数学模型,从而使得传统的定位原理从定性描述上升为数学定量表示,并为计算机辅助夹具设计系统的开发提供了基础理论.另一方面,以定位原理数学模型为基础,在UG软件系统环境下实现了夹具约束工件自由度分析系统的二次开发.     

基于刚体运动学的工件自由度分析方法

夹具设计最主要的任务就是将工件精确定位。在定位过程中,首先必须合理地约束工件自由度;其次在自由度受到约束的方向上,工件也只能在规定的范围内变动。因此,分析工件的自由度约束情况是复杂定位方案设计甚至整个夹具设计的关键所在。基于刚体运动学,文章建立了定位原理的数学模型,以定量分析工件自由度的约束情况。从而使得传统的定位原理从定性描述上升为数学定量表示,为计算机辅助夹具设计系统的开发提供了基础理论,并首次在UG软件系统环境下实现了夹具约束工件自由度分析系统的二次开发。     

工件位置加工误差的分析与建模

主动寻位与状态记忆安装技术(InitiativeLocatingandStateMemory,简称IL&SM)是一种新型的工件安装方法。通过运用齐次坐标变换原理分析了多工序转换过程中,IL&SM箱体对工件上特征间位置精度的影响,并给出了描述工件位置误差的通用数学模型,最后通过实例说明了位置误差建模方法的应用。研究结果将为消除箱体原始误差对工件加工精度影响,从而为进一步实现误差补偿提供理论参考依据。     

多腔缸体零件端面铣削加工的高精密夹具设计及其优化

针对发动机多腔体缸体的结构复杂和刚度小的问题,对该缸体铣削端面加工工序确定高精密夹具的定位和夹紧方案.在初步分析夹具方案之后,运用有限元法对夹具的主要零件进行了变形分析和计算,并在此基础上对夹具结构进行了优化,最终确定了高精密夹具设计新方案.结果表明优化得到的设计方案优于经验设计方案,提高了夹具的定位和夹紧精度,从而保证了加工质量,在实际生产中效果良好.     

Off-line modelling and planning of optimal clamping forces for an intelligent fixturing system

An intelligent fixturing system (IFS) for machining aims to adaptively adjust the clamping forces to achieve minimum deformation of the workpiece according to the cutter position and the cutting forces. This paper presents the concept, architecture, control scheme, models and methodologies for an IFS. Using off-line simulations and on-line experimental verifications, the performance of the proposed IFS is evaluated and verified. As adaptive clamping forces appropriate to the dynamic machining environment are employed, the IFS offers higher quality of machined parts and greater robustness to disturbances. This system is suitable for application in high-precision machining environment as well as flexible manufacturing systems (FMS).     

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.     

Contact condition modelling for machining fixture setup processes

Manufacturing automation often requires high precision and highly accurate equipment to achieve satisfactory performance. In many cases, precision and accuracy depend highly on the surface contact conditions between machine components. Described in this paper is the modelling of the response frequency of a modular fixturing system with multiple components in contact, and it has demonstrated that it is possible to monitor the contact conditions based on a fixture system's dynamic response frequencies. The virtual spring element based on the Hertz theory is used to recapitulate the fixture contact conditions in the finite element modelling. Possible contributing factors to contact conditions, such as material properties, surface finish, hardness and the contact area between the workpiece and fixture device, are investigated in the estimation of the virtual spring constant. Experimental analysis is also conducted to verify the analytical model. The application of this model can be used for control, monitoring, and design of general clamping devices in many manufacturing processes.     

Electromagnetic incremental forming (EMIF): A novel aluminum alloy sheet and tube forming technology

Large parts cannot be shaped by conventional electromagnetic forming method due to the limitation of the strength of working coil and the capacity of capacitor bank. In this paper, based on the principle of single point incremental forming, a new method named electromagnetic incremental forming (EMIF) has been proposed. The method makes use of a small coil and small discharge energy to cause workpiece local deformation in a high speed. Finally, all local deformations accumulate into large parts. For the electromagnetic incremental sheet forming, the effect factors of processing parameters namely discharge voltage, vent hole, discharging times in a fixed position and the number of discharge region, on final sheet shape are investigated by using AA3003 aluminum alloy parts. In addition, two different simulation strategies are proposed to predict electromagnetic incremental sheet and tube forming process. For method 1: the technology like “birth–death element” is used to indirectly describe the movement of the coil and the morphing technology is used to make the air change with the workpiece deformation. For method 2: the coil can directly move to a special position and the remesh technology is used to consider the effect of the workpiece deformation and the movement of coil on magnetic analysis. It is found that method 1 cannot be used for electromagnetic incremental sheet forming process if overlap region exists in two adjacent discharge regions. However, method 1 can successfully predict electromagnetic incremental tube forming. And method 2 can be used for electromagnetic incremental sheet or tube forming. Both of the experimental and simulation results demonstrate that this new technology is feasible to produce large part.