机床主轴支承距最佳值的简便计算法

机床主轴支承距的合理选择,是获得主轴部件最大静刚度的重要条件之一。 为要获得主轴部件最大静刚度,要从力学的受力和变形的角度出发,确定主轴受力后的轴端位移。使主轴轴端位移在受力时达到最小值的主轴主承距就是最佳值。目前,求此最佳位大致有两种方法:一是根据经验值推荐取l=(1～5)a1(式中,l-两支承间的距离; a-主轴悬伸量,参见文献[4]); 二是根据受力时轴端位移与支承距的关系式y=f(l)(各受力情况下具体关系式见文献[1])来确定支承距最佳值l0。第一种方法是近似的,第二种方法目前的主要问题是,如何快速而准确地确定一个一元三次方程的…     

数控机床主轴部件最佳支承距计算软件的编制

在数控机床中,主轴部件最佳支承距对主轴部件的性能影响很大,因此对主轴部件最佳支承距的计算是主轴部件设计中相当重要的工作。编制计算机软件来做主轴部件最佳支承距的计算,既可以提高工作效率,使得过去复杂的计算在数秒内轻松解决,同时可将设计人员从繁杂的重复劳动中解脱出来。     

机床主轴部件的实用计算与分析

本文讨论了有关参数对主轴部件静刚度的影响，设计了计算线图。它可用来迅速确定主轴部件的实际刚度、可能达到的最佳刚度和最佳支承距。本文建议：主轴部件支承距的合理范围为最佳支承距的１．４～１．６倍，以兼顾静刚度和主轴结构布局的要求。     

应用有限元法推导三支承机床主轴的静变形和支反力的计算公式

为了提高机床主轴部件的刚度和抗振性,主轴常采用如图所示的三支承形式,前后支承是主要的,中间支承起辅助作用,有一些游隙。但在目前设计简化计算过程中,仍常将三个支承简化为刚性的。先将主轴采用当量直径法简化为等截面的形式,利用三弯矩方程,或梁的变形条件(即中间支承处的烧度为零,或为某一给定值)列出方程式求出中间支承的支反力,再去掉中间支承,代之以该处的支反力,然后用两支承轴的变形计算公式计算其变形值。这种方法计算繁琐,工作量大。我们用有限元法推出了如下一套简单的计算方法。 一、计算公式的推导 首先,利用当量直径法将主…     

机床变截面主轴刚度的计算

通常采用虚梁作图法计算机床变截面主轴的变形或刚度,由于比较麻烦使用不够普遍。但对主轴进行刚度核算时,通常只需要知道主轴端部的挠度y和前支承处的转角θ就够了。为此本文推荐一个基于能量法的计算公式,可以使计算过程大为简化。这里不来证明,仅通过下图的例子介绍实际应用的方法。 一、主轴挠度 y的计算 如图中a所示,按直径变化处及支承处把轴分成n段:i=1,2,……m,m+1,……n;其中0～m在两支承之间;m+1～n为主轴悬伸部份(本例m=3,n=5),则挠度y可控下式计算:式中:P——载荷,kgf; E——弹性模量,对钢取E=2.1×106 Il——第i段轴之惯性矩…     

有限元静态特性分析在主轴上的应用

1．构建几何模型 CKS6125主轴是一种阶梯轴,具有中空、多支承的特点。主轴承受多种载荷,在四个轴承支承下高速旋转,因此,该主轴是一个较复杂的超静定梁结构。虽然主轴轴承的刚性不是一个定值,而是轴承所受载荷（主轴支反力）的函数,但由于主轴的结构对称,形状简单,为了方便计算,将其作为空间弹性梁处理。     

机床主轴的刚度计算

本文推荐利用能量法(莫尔积分)及叠加原理导出的公式计算机床主轴前支承处转角及悬伸端挠度的计算方法。本方法简单明了,便于实际应用。 一、主轴悬伸端载荷P所产生的主轴前支承处转角θp及轴端挠度yp。 如图1所示,按直径的变化,在两支承间将轴分为几段,即i=1,2,…,n。将轴的悬     

风电机组主轴热固耦合特性研究

通过热固耦合方法,进行了风电主轴温度场及热应力场分析,考虑了载荷、支承结构和支承跨距3个因素,完成了对主轴热应力影响因素的研究。发现了主轴次表面下40 mm范围内受环境温度影响大,承受交变应力幅度大;针对后端浮动状态或者为单轴承支承状态,发现了主轴受热产生轴向变形大,说明了消除温度场变化对齿轮箱行星轮系产生浮动影响;通过主轴支承跨距变化的分析,得出了约束端材料应力应变状态,提出了在选择主轴支承跨距时,需要计算温度场变化引起应力集中处平面应变状态情况。     

弹性支承轴的变形计算软件

一、前言 人们对计算轴受力后的变形与确定最佳支承跨距作过许多研究,引入了种种简化假设:支承是刚性的,只有两个或三个支承,轴是等直径的,受力情况是特定的等等。本文不需要这些假设,运用有限元法编制了可单独使用的计算与图形显示软件,可以方便地在PC机上计算弹性支承轴的变形、支承跨距优化、兼作横振固有频率计算,并且用图形显示轴在受力情况下的变形。     

基于PLC的阶梯轴精密磨削柔性控制

根据阶梯轴纵磨法的磨削加工过程,设计了以PLC为控制器,以热压氮化硅陶瓷轴承电主轴为砂轮主轴单元的高速磨削系统,采用球顶尖作为工件支承,实现阶梯轴磨削后的圆度误差在线测量。成功的利用了PLC的E点控制和原点返回控制功能,实现阶梯轴磨削过程的柔性控制。实践证明,此种方案加工精度高、生产效率高、灵活性好。     

Dynamic characteristics of spindle with water-lubricated hydrostatic bearings for ultra-precision machine tools

A key component of ultra-precision machine tools is the spindle. The motivation for this study was to improve machining accuracies in precision cutting and grinding by pursuing improvements in the spindle characteristics by designing a sophisticated spindle with water-lubricated hydrostatic bearings. The static bearing stiffness of the developed spindle was investigated in previous studies. In addition to the static bearing stiffness, the dynamic characteristics regarding bearing stiffness also affect significantly on the machining results. In this study, dynamic characteristics of the developed spindle with water-lubricated hydrostatic bearings were investigated via simulations and experiments. Not only bearing dynamics but also rotor dynamics were considered in this study.In the simulation studies, the spindle dynamic characteristics were analysed based on the transfer matrix method. A spindle rotor supported with hydrostatic bearings was represented by discrete sections of the rotor. The mathematical model of transverse linear vibrations of the spindle rotor was derived with distributed parameters for these discretized rotor sections. As a result of the analysis on the amplitude-frequency characteristic, radial displacements of the rotor due to bearing displacement and bending deformation were defined. Then, the frequency characteristics were represented with Nyquist plots. Resonant frequencies and amplitudes formation in the transverse vibration of the rotor were determined. The influence of rotor bending deformations on spindle compliance was assessed. Furthermore, the study examined the influences of the supply pressure of the lubricating fluid, radial clearance and journal diameter of the hydrostatic bearings on the amplitude of the rotor vibration, and the resonance frequency of the system.Furthermore, the dynamic characteristics of the spindle were examined experimentally. The simulation results were in good agreement with the actual spindle dynamics obtained experimentally. The influence of the structural parameters of the rotor and the operating parameters of the bearings on the spindle dynamic characteristics was also determined. It was verified that the amplitude of the vibration of the rotor overhang part was dominantly affected not by bearing stiffness but by bending stiffness of the bearing journal of the front bearing and the length of the rotor overhang.Then it was verified that the resultant displacement of the rotor in the radial direction due to the influence of the bearing characteristics and the structural effect of the rotor is significantly small. Practical recommendations to improve the spindle design in terms of the dynamic characteristics of the spindle with water-lubricated hydrostatic bearings were also derived.     

高速主轴离心膨胀及对轴承动态特性的影响

以高速主轴系统为对象,将主轴转子和轴承内圈分别等效为等截面梁和空心圆盘,计算离心力作用下主轴转子和轴承内圈的径向弹性变形,并分析主轴转子与轴承连接状态随转速升高的变化趋势。考虑旋转部件的离心膨胀变形,建立高速主轴轴承动力学模型并进行试验验证。在此基础上,研究离心效应对主轴轴承径向预紧状态的影响,揭示高速主轴轴承动态特性随转速的变化规律。研究结果表明,离心力引起的径向膨胀变形使滚动体与轴承内、外圈之间的接触角减小,接触力增加。主轴轴承的轴向刚度和径向刚度均随转速的升高而降低。轴承内圈的离心膨胀变形对轴承轴向刚度的影响可以忽略不计,而能在一定程度上提高轴承的径向刚度。     

基于材料热特性的轴承预紧力自调节设计方法

采用滚动轴承支承的机床主轴在转速上升过程中摩擦发热产生温度变化,引起轴承预紧力变化限制了机床转速。提出材料热特性轴承预紧力自动调节方法,该方法是根据温度变化时金属材料受热伸长的特性,通过分析机床主轴转速上升时摩擦功率损耗产生的热量,建立主轴温度场模型。采用有限元计算主轴工作温升引起的热变形,按照两种金属材料受热伸长的差值,建立温差与位移关系的数学模型,并求解应用双金属材料结构设计参数。仿真计算结果表明,通过使用轴承预紧力自调节方法,可以有效地扩大机床转速范围,应用在加工中心的主轴上,主轴最高转速由2.5 kr/min 提高到了3 kr/min,取得了明显的效果。     

深沟球轴承的载荷分布与刚度特征研究

采用有限元法计算了"奇压"与"偶压"两种受载形式下深沟球轴承的静力学响应。对比讨论了轴承内接触应力分布、轴承变形及刚度的变化特征。结果表明当外载荷达到某一值时,关键滚动体与外圈滚道接触中心的接触应力明显大于与内圈滚道接触中心的接触应力,并随着载荷的增加,这个趋势越发明显;两种受载形式下,轴承的位移与刚度表现出明显的差异,奇压形式下,轴承的径向位移小于偶压形式下的径向位移,而奇压形式下的轴承刚度则大于偶压形式下的刚度;相同载荷作用下,静力学方法计算的轴承径向位移小于有限元法计算结果。     

高速铁路轴承试验台的主轴结构优化

建立了高速铁路轴承试验台主轴的参数化有限元模型,利用有限元分析软件ANSYS对主轴进行了模态分析,初步判定主轴会发生共振。对主轴结构进行了优化计算,结果表明,该方法确立了支承轴承的位置,主轴在自重减轻的情况下提高了其一阶固有频率,改善了主轴的动态性能,并且有效地避开了共振区。     

高速精密角接触球轴承零件热位移分析

高速机床主轴的精密角接触球轴承将产生大量的摩擦热。轴承摩擦热是限制机床主轴高速性能、刚性性能和高功率性能的最主要原因。大部分的轴承摩擦热通过传导进入轴承零件,造成温度上升,使轴承零件产生一定的热位移,影响机床加工精度和质量。当轴承零件的温度处于不稳定状态时,轴承内部的接触压力迅速增大,产生更大的摩擦热,从而使轴承立即出现热咬合、烧伤等失效形式。在某些特殊的高温应用场合,轴承工作温度较高,应考虑工作温度产生的轴承零件热位移,合理选择轴承装配游隙和安装方式。因此,轴承零件热位移计算对滚动轴承设计与应用,尤其是…     

Dynamic Analysis of Plain Bearings in a Positive-Displacement Rotary Compressor

This paper discusses the dynamic performance of plain bearings in a positive displacement rotary compressor. It includes dynamic bearing loads produced by rotor unbalance and cyclical loads produced by gas compression forces acting on the rotor. With the aid of the short-bearing approximation, bearing center loci and oil film pressure distributions are determined. The optimum location of oil film feed groove for the bearings of such a compressor is discussed.     

卧式数控加工中心主轴热误差及刀尖轨迹分布

应用热力学经典理论对主轴系统热源分布及传热方式进行了分析,并对主轴温度场和机床热变形进行 了试验研究.研究发现,主轴的转动及其与轴承的摩擦热是主要热源之一,并且主轴热变形与温度有直接关系.通过对不同转速下的刀尖点轨迹进行分析发现,同一轴向上不同位置测点的热变形及同一位置不同轴向测点的热变形分别在局部细节和宏观趋势上存在...     

高速电主轴轴承热分析与实验研究

根据高速电主轴角接触球轴承中滚动体的运动情况,分析其受力状态,并考虑轴承预加载荷对滚动体在高速旋转状态下陀螺力矩的平衡效果,应用Palmgren经验公式计算轴承整体的摩擦热,然后依据传热学理论建立轴承的温升热模型,并用热网络法建立其热阻抗网络图,最后用120MD60Y6油雾润滑型电主轴的轴承进行试验验证.结果表明,轴承温升主要受转速、润滑油量、供气压力及载荷的影响,在主轴启动的初始阶段温升变化最快,且润滑油量和供气压力对轴承温升有一个最佳的适用范围.     

An integrated prediction model for the dynamics of machine tool spindles

ABSTRACT

The predictility of dynamics of the machine tool spindles is essential for machining precision. During machining, the machine tool components and the cutting process interact with each other. Accordingly, it is necessary to take the process-machine interaction effects into account in order to predict the spindle's dynamics accurately. This paper presents an integrated model for the prediction of a spindle's dynamics. The model synthesizes the interactive influence between machine dynamics and forces in grinding process. The thermo-mechanical model of the spindle with angular contact ball bearings was built by using the finite-element method. The analytical model was used to calculate the process forces. A coupled simulation was adopted to accomplish the interactive process between the two models. Basing on the integrated model, the bearing stiffness, the natrual frequency, the spindle tip stiffness and deformations of a grinder's spindle were investigated. The prediction of the deformation fluctuations at the spindle tip due to process-machine interaction was also achieved.