新型高阻尼机床主轴的研制及其综合性能试验

本文提出了一种新型的高阻尼机床主轴结构,并对其动态性能、静刚度和热态性能进行了深入研究。试验结果表明:这种在原机床主轴的支承部位增设阻尼圈的高阻尼主轴结构可以在静刚度和热态性能下降很小的情况下,显著地改善主轴系统的动态性能。     

正弦激振测定轴承的刚度和阻尼

在研究机床主轴系统动态性能时,必须知道轴承的支承参数,即,径向刚度K、径向阻尼C_r、角刚度K_c和角阻尼C_a,见图(1)。目前这些参数值,往往是通过试验确定。在结构分析中,刚度值可以通过静态或动态试验来测定,但阻尼系数的识别只能用动态方法测定,所以一般采用动态试验同时测定刚度和阻尼。在被测系统上施以单频的正弦扫频激振或是宽频的瞬态的随机激振,测出系统在激振力F的响应,根据参数识别的基本理论,就可求出系统的各参数。笔者在对某型机床主轴特性进行研究时,为了建立可供电算的主轴系统力学模型,采用一些     

机床—主轴耦合系统动力学建模与模型修正

复杂精密零件的加工对机床装备的性能不断提出新的挑战。为了保证零件加工精度,有必要在设计阶段对机床整机的动态特性进行精确预测和评估。以机床主轴系统为研究对象,介绍一种机床—主轴系统耦合动力学模型,并指出该模型中存在结合面动态特性参数的辨识问题。为了修正该耦合模型,提出一种基于频率响应函数的有限元模型修正技术。采用包含平动自由度(Degree of freedom,DOF),转动DOF以及平动与转动耦合DOF的刚度矩阵来描述结合面的动态特性,通过测量结合面处的动态响应数据,辨识出高速主轴与机床之间结合面的刚度参数,从而达到模型修正的目的。试验结果表明,修正后的机床—主轴耦合模型反映出了机床结构对主轴动态特性的影响,能较好地预测主轴安装到机床上以后的动态特性,从而为高性能机床的数字化设计与制造提供理论依据。     

VMC为解决热伸长而努力

Fadal公司的VMC3020型重型机床,是一种高性能、适用于重切削加工的机床,主轴具有高扭矩。其X、Y、Z轴的行程分别为760mm、508mm和508mm。机床为铸铁床身,其导轨为方形结构,因此具有良好的阻尼性能。机床有一个自动双速主轴驱动系统,并行处理的控制系统和直径40mm的滚珠丝杠,保证快速进给和工作速度,而     

基于虚拟设计的铣头式机床主轴结构动态特性仿真分析

铣头式机床的主轴是多组件、复合支承的特殊结构，影响机床动态性能。在虚拟设计的数字样机上采用有限元法和模态综合技术对主轴进行了动态特性仿真分析找出薄弱环节。根据分析结果。修改和优化主轴结构设计。     

应用有限元分析系统计算车床主轴的动态特性

机床动态特性是影响机床性能的重要因素,是在机床设计时必须要考虑的问题,模态分析主要用于确定结构或机器部件的振动特性。建立主轴的三维有限元模型,利用大型有限元分析软件AN SY S,对主轴部件进行了模态分析,得出了主轴前五阶固有频率和振型。了解主轴部件的各阶振动模态的特点,对于我们研究主轴部件的动态特性是十分必要的,有利于机床主轴系统的整体设计及其制造。     

期刊论文摘要

根据阻抗曲线识别机床主轴滚动轴承的动态参数——陕西机械学院只辉、张华容、郭涛,《机床》1981年,第3期,第16～20页 轴承作为机床主轴系统的支承部件(子系统),它的动态特性是构成机床主轴系统动态特性的一个重要参量。应用机械阻抗方法和系统识别技术确定其动态参数(刚度、阻尼等)是至今唯一较理想的有效方法。     

基于能量分布的机床整机动态特性优化方法

基于机床结构中的能量分布,在准确建立立式加工中心整机有限元模型的基础上提出一种整机动态性能优化方法。采用弹簧阻尼系统等效结合部的接触特性,基于辨识的结合部等效刚度和阻尼值在Ansys中建立了立式加工中心整机有限元模型,对整机进行模态分析和谐响应分析。通过整机模态试验验证了该有限元模型的准确性,并根据有限元分析与试验结果确定整机的薄弱模态。计算薄弱模态下整机、结合部的弹性能以及结合部在整机中的弹性能分布率,以分布率较高的结合部作为薄弱结合部。基于薄弱结合部的等效接触刚度提出优化方案,优化后薄弱结合部的弹性能分布率明显降低,主轴轴端的动态响应幅值降低,从而使整机动态性能得到改善,验证了该优化方法的可行性。     

液体动静压电主轴关键技术综述

液体动静压主轴以其高回转精度、高动态刚度、高阻尼减振性和长寿命等性能优势,在高速精密机床领域获得广泛应用,但进一步适应超高速超精密加工需要,发展成为将机床主轴与高速电动机功能从结构上融为一体的液体动静压电主轴,还需解决高速化和结构集成化带来的轴承温升控制和电机性能优化等技术难题,需进一步从机理层面研究轴承特性和电动机高频电磁损耗等科学问题。因此有必要对现有研究成果进行系统分析和深入总结。回顾液体动静压机床主轴轴承技术的发展历史;从轴承油腔结构、节流器、轴颈偏斜、轴瓦弹性变形、轴承副表面形貌、液体惯性效应、热效应、润滑介质可压缩性及非牛顿特性、水润滑动静压轴承等方面,对影响液体动静压电主轴轴承特性的关键技术进行逐一分析和评述;从高速电主轴对电动机几何特性、转速—力矩特性、热特性、振动及噪声特性的要求等角度,全面评述电动机性能的电磁参数设计方法、电磁损耗机理及计算方法和电磁损伤故障防治技术;具体分析动静压电主轴整机特性优化中的关键技术难题;对液体动静压电主轴技术的未来发展趋势进行预测和展望。     

卧式加工中心主轴静刚度特性的试验研究

介绍了卧式数控加工中心主轴的静刚度特性所开展的试验研究.根据预加载荷测得的静刚度试验数据,应用最小二乘法拟合得到主轴在加载和卸载时的静刚度曲线.研究后发现,主轴卸载刚度大于加载刚度:相同结构尺寸机床,主轴最高转速低的机床主轴静刚度要高于主轴最高转速高的机床;相同最高转速和结构的机床,尺寸大的机床主轴静刚度要高于尺寸小的...     

DYNAMICS ANALYSIS OF SPECIAL STRUCTURE OF MILLING-HEAD MACHINE TOOL

The milling-head machine tool is a sophisticated and high-quality machine tool of which the spindle system is made up of special multi-element structure. Two special mechanical configurations make the cutting performance of the machine tool decline. One is the milling head spindle supported on two sets of complex bearings. The mechanical dynamic rigidity of milling head structure is researched on designed digital prototype with finite element analysis（FEA） and modal synthesis analysis （ MSA ） for identifying the weak structures. The other is the ram structure hanging on milling head. The structure is researched to get dynamic performance on cutting at different ram extending positions. The analysis results on spindle and ram are used to improve the mechanical configurations and structure in design. The machine tool is built up with modified structure and gets better dynamic rigidity than it was before.     

Effects of preloads on joints on dynamic stiffness of a whole machine tool structure

The machine tool joint is a very important factor in the overall machine tool dynamic analysis, and it has great effects on the machining performance of a machine tool. As a very important operation parameter, preload greatly influences the stiffness and the damping of a machine tool joint. This paper presents the effect of preload on the dynamic stiffness of the spindle nose of a horizontal machining center. By discussing types and distribution of machine tool joints, studies on the joints of ball screws, linear guides and bolts are carried out. The influence of preload on the axial stiffness of a ball screw is calculated based on Hertzian contact theory and the effect of pretightening moment on pressure of bolt joint is discussed, while the dynamic stiffness and the damping of a linear guide are identified by an optimum algorithm with the simulated and experimental results. A finite element model (FEM) of the whole machine tool structure considering the effects of different joints is created and verified against the test results, and then the influence of preloads on ball screws and linear guides is predicted. Results indicate that preloads on machine tool joints have significant effects on the dynamic stiffness of the spindle nose.     

Analysis of the machining stability of a milling machine considering the effect of machine frame structure and spindle bearings: experimental and finite element approaches

Chatter vibration has been a troublesome problem for a machine tool toward the high precision and high-speed machining. Essentially, the machining performance is determined by the dynamic characteristics of the machine tool structure and dynamics of cutting process of spindle tool. Prediction of the dynamic behavior at spindle tool tip is therefore of importance for assessing the machining stability of a machine tool at design stage. This study was aimed to evaluate the machining stability of a vertical milling system under the interactive influence of the spindle unit and the machine frame structure. To this end, a realistic finite element model of a vertical milling tool was generated by incorporating the spindle-bearing model into the head stock mounted on machine frame. The influences of the dynamics of spindle-bearing system and the machine frame structure were investigated respectively. Current results show that the machine tool spindle system demonstrates different dynamic behaviors at different frequency ranges, which are also characterized as structural modes and spindle modes, respectively. In particular, the maximum compliance of spindle tool tip was found to occur at the bending vibrations of spindle shaft and vary with the preload amount of spindle bearing. The machining stabilities were predicted to different extent, depending on the exciting modes which could be related to the influences of machine frame and spindle unit.     

陶瓷轴承主轴单元动特性的实验研究

对陶瓷轴承主轴单元的动态性能特点进行了实验研究。研究发现,在相同预紧和脂润滑条件下,陶瓷轴承主轴单元的阻尼系数比钢轴承主轴单元小,主轴端部的直接动柔度比钢轴承主轴单元大。研究结果为采用陶瓷轴承主轴单元的高速和超高带数控机床的动态设计提供了实验依据。     

Dynamic Performance of the Ceramic Bearing Spindle Unit

Dynamic performance of a ceramic bearing spindle unit is studied in this paper. It is found that the damping coefficients of the ceramic bearing spindle unit are smaller than those of the steel bearing one,direct mobility in the front nose of the ceramic bearing spindle unit is larger than that of the steel bearing one after the experimental modal analysis for a standard spindle unit. The experimental results provide a scientific basis for the dynamic design of high speed and extra-high speed machine tool with the bearing spindle units.     

数控机床主轴部件动态优化设计

在对某型数控车床进行空运转、切削及模态试验的基础上，确定了机床主轴部件动刚度薄弱是引起机床切削的结构颤振方面的原因。据此，建立了机床主轴部件的有限元动力学模型，并对主轴部件进行了静、动特性的计算和动态优化设计。     

基于改进PSO算法的数控机床主轴优化设计

通过分析主轴结构和加工过程中受载变形情况, 建立了主轴优化设计的数学模型。根据邓克莱法计算得到的一阶固有频率近似值,引入动态约束条件 。针对传统优化设计方法在解决主轴优化设计中出现的问题,引入粒子群优化 (PSO) 算法,并提出了一种惯性权重值适应性递减的粒子群（ADW）算法。将ADW算法用于数控机床主轴优化实例中,得到主轴结构参数优化组合。研究结果表明,运用所建立的主轴优化设计数学模型及改进粒子群算法可以得到主轴结构参数优化组合,充分显示了该研究方法的有效性。     

挤压液膜阻尼器在精密孔磨削中的应用

采用液膜阻尼技术研究精密孔的加工,按照达朗贝尔原理建立了液膜阻尼砂轮主轴运动微分方程,对挤压液膜阻尼器作用下的砂轮主轴中心运动轨迹进行了仿真,基于仿真结果设计了带挤压液膜阻尼器的内圆磨床砂轮主轴并进行了磨削试验。试验结果表明,设计合理的挤压液膜阻尼器对砂轮主轴具有优良的减振作用,可使砂轮主轴的振动减小30%～45%、精密孔的加工质量提高10%～20%、机床的工作效率提高15%～25%,在机械加工领域具有十分重要的研究价值和广阔的应用前景。