车床夹具设计及应用研究

在生产过程中,用镗铣床加工连杆零件整个工序繁琐,加工辅助时间长,生产效率低,生产成本高,不符合工厂的生产需要。针对此种情况,设计出一种车床辅助夹具,使工件和夹具的配合在保证加工精度的同时,加工效率得到极大的提高。     

车床夹具在吊环件中的应用

在生产过程中,尝试用数控车床加工以往在其它设备上生产的吊环工件,针对此种情况,设计出一种车床辅助夹具使工件和夹具的配合,既可保证加工精度,又大大提高了加工效率.     

机床夹具制造中组合加工法的应用与实践

组合加工法在夹具制造工艺方面上明显有别于装配调整法,其基本原理是将夹具作为一个整体对待,对有位置精度要求的导向结构或定位结构,安排在夹具组装后进行加工,以最大限度地减少各元件之间的累积误差,提高夹具制造精度。现以典型实例为例,论述了组合加工法在夹具制造中的应用过程,并总结了应用这种工艺方法制造的夹具在图样设计的主要特点。大量的实际应用表明,组合加工法是保证夹具制造精度的最简便有效的工艺方法。     

装配加工法在保证夹具制造精度中的应用

装配加工法在夹具制造工艺方面上明显有别于装配调整法,其基本原理是:将夹具作为一个整体对待,对有位置精度要求的导向结构或定位结构,安排在夹具组装后进行加工,以最大限度地减少各元件之间的累积误差,提高夹具制造精度。文章通过典型实例论述了装配加工法在夹具制造中的应用过程,并总结了应用这种工艺方法制造的夹具在图样设计方面的主要特点。大量的实际应用表明,装配加工法是保证夹具制造精度的最简便有效的工艺方法。     

夹具设计中常见的问题

在夹具设计过程中，对于被加工零件的定位、夹紧等主要问题，设计人员一般都会考虑的比较周全，但是，夹具设计还经常会遇到一些小问题，这些小问题如果处理不好，也会给夹具的使用造成许多不便，甚至会影响到工件的加工精度。我们把多年来在夹具设计中遇到的一些小问题，归纳如下：     

基于精度设计理论的机床夹具CAD设计系统研究

以建模分析方法和综合定位误差方程,系统研究夹具定位误差的控制;应用三面基准精度设计方法,建立夹具精度控制系统;以控制理论为基础,研究夹具在工艺系统中动态误差的控制.本课题兼顾精度设计和结构设计的简便易行夹具CAD设计系统,应用VB技术和对AutoCAD的二次开发,实现在AutoCAD平台从计算机辅助绘图向计算机辅助夹具设计的拓展.     

装配加工法在保证夹具制造精度中的应用

装配加工法在夹具制造工艺方面上明显有别于装配调整法,其基本原理是,将夹具作为一个整体对待,对有位置精度要求的导向结构或定位结构,安排在夹具组装后进行加工,以最大限度地减少各元件之间的累积误差,提高夹具制造精度。以典型实例为例,论述了装配加工法在夹具制造中的应用过程,并总结了应用这种工艺方法制造的夹具在图样设计的主要特点。大量的实际应用表明,装配加工法是保证夹具制造精度的最简便有效的工艺方法。     

凹球面的弹簧靠模车床夹具设计

在车床加工中,当利用车床靠模加工某带有凹球面的工件时,由于该工件的表面粗糙度要求较高,对型面的形状精度要求更高,传统的车床靠模加工中与凹球面相接触的是聚氟乙烯膜片,如果凹球面精度达不到要求,将严重影响膜片的使用寿命和产品的计量精度.     

数控车床用多类型弯头加工夹具

用镗铣床加工弯头件时,生产效率低,生产成本高,不能满足工厂的生产需要。文中设计出一种车床辅助夹具,使工件在夹具的配合下,在保证加工精度的同时,极大地提高了加工效率。     

机床夹具的装配加工法

目前困扰有关生产厂家的一个突出问题是有相当数量的机械零件的制造精度达不到设计要求。对成批生产而言,机械零件的制造精度在很大程度上取决于加工该零件的机床夹具能否达到夹具设计精度要求。 从目前状况来看,夹具设计精度保障方法依然是采用装配调整法,而企业的夹具设计资料是装配图加零件图。这就决定了夹具制造只能象一般机械制造那样,先按零件图制造出所有零件,然后组装,再设法通过调整来满足装配图提出的各种尺寸及形位公差要求。据笔者多年的实践,对于绝大多数夹具来讲,这种装配调整法很难保证夹具装配精度的要求。为此,笔者改用装配加工法来实现夹具的高精度要求。 装配加工法过去已有应用,例如减速箱的齿轮轴承孔的镗削。笔者只是将这种方法在夹具制造中加以     

The study of fixture stiffness part I: a finite element analysis for stiffness of fixture units

This paper presents a systematic finite element model to predict the fixture unit stiffness by introducing nonlinear contact elements on the contact surface between fixture components. The contact element includes three independent springs: two in tangential directions and one in the normal direction of the contact surface. Strong nonlinearity is caused by possible separation and sliding between two fixture components. The problem is formulated by the penalty function method and is solved by the modified Newton--Raphson procedure. The model was validated by two cases of analysis of a linear cantilever beam and a simple fixture unit with two components. Results are in agreement with the corresponding analytical solution of beams and the previous experiment results for fixture in the literature.     

真空夹具设计应用及静力接触有限元数值模拟

真空夹具适于飞机壁板、框、翼肋等薄壁类铝合金整体结构件机械加工。在介绍真空夹具结构特点、工作原理基础上,分析了吸附过程中工件受力状况。结合某型飞机升降舵梁零件加工工艺,详细分析了真空装夹方案的选取、结构设计。利用有限元法,对真空夹具进行静力接触数值模拟,研究装夹过程中零件受力变形情况,仿真结果为设计提供有效理论数据。     

隔离体法在有限元接触分析中的应用

这里针对施加初始预紧力时超高压密封容器有限元整体接触计算不收敛的情况,给出一种近似的计算思路—隔离体法。运用此方法,建立了该容器密封接触计算的等效隔离体模型,并运用有限元软件对该模型进行了计算,同时利用密封线比压判断准则对计算结果进行等效判断。经工程试验验证,计算结果合理,表明该近似方法的有效性。     

有限元法在机械结构模态分析中的应用

运用有限元法对机械结构进行模态分析可以求出结构的固有振动特性,获得避免共振现象产生的工作频率范围,同时提出改善结构模态特性的方法。文章运用有限元分析软件ANSYS分析了某机床床身的前8阶固有频率和振型,提出了适合加工的主轴转速范围和改善床身结构模态特性的方法。研究实例表明:有限元法具有简单、快速、直观的特点,是一种对机械结构进行模态分析的有效方法。     

有限元和断裂力学在结构故障诊断中的应用

冶金起重机由于其工作环境恶劣，工作级别高，起重量大以及结构相对复杂，使其金属结构很容易出现故障，其中最常见、最危险的是出现疲劳裂纹。某大型钢厂发现3台不同厂家制造的140t和125t铸造起重机主梁副腹板的舱门拐角处的焊缝及腹板母材开裂，母材裂纹最长者达150mm,     

有限元法在金属高速切削加工技术中的应用

阐述了有限元法在切削过程、切削加工表面残余应力计算、切削热和切削温度、以及切屑形成机理等高速金属切削加工中的应用,总结分析了有限元法在这些方面研究取得的成果及不足,展望了高速切削加工技术的研究方向.     

Recent developments on machining fixture layout design, analysis, and optimization using finite element method and evolutionary techniques

A review of the recent development of the machining fixture configuration/layout is presented in this paper. The literature review is mainly focused on the recently developed optimal fixture configuration under the dynamic conditions of the workpiece. In this review paper, the fixture design, fixture analysis, fixture synthesis, fixture layout design, optimization of fixture layout design, various optimization algorithms, and case studies of two- and three-dimensional workpiece geometries under dynamic conditions have been emphasized specially. The further scopes of the research are finally summarized.     

Elastic deformation of a fixture and turbine blades system based on finite element analysis

Finite element analysis (FEA) has been used to recapitulate the interactions between fixtures and components over the last decade. Most of the researches were focussed on the 3-2-1 fixture for components with regular geometry using point-to-point contact elements, where the fixture element is represented by a point-contacting component. Due to predicable behaviour of the fixture–component pair, such a point-to-point contact representation may be sufficient. However, when components with complex geometry, e.g. B-spline surfaces, which are widely used in the automotive and aero-engine industries, are of interest, the point-to-point method can no longer be satisfactory. This paper proposes a method of FEA on a system of a fixture and turbine blades by considering the complex contact geometry and complicated contact status of fixture–component pairs using surface-to-surface contact elements. A complete procedure of FEA modelling including geometry simplification, contact modelling, stiffness of locators, mesh generation, boundary condition and loading sequence is explained in detail. Having verified the FEA prediction of the elastic deformation with the displacement of the workpiece measured by coordinate measurement machines (CMMs), the influential factors of deformation, such as friction and machining directions, are analysed.     

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.     

CAD/CAE集成中参数化有限元建模的研究

介绍CAD/CAE集成中参数化有限元建模的重要性和实际存在的问题。阐述几何模型转化为有限元模型的理论,提出一种基于VC 和ANSYS接口技术建立参数化有限元模型方法,并以渐开线圆柱直齿轮有限元模型的建立为例,描述了参数化有限元建模过程,并设计了便于用户操作的参数输入界面。