Effect of Working Position on Vertical Motion Straightness of Open Hydrostatic Guideways in Grinding Machine

Hydrostatic guideways have various applications in precision machine tools due to their high motion accuracy. The analysis of motion straightness in hydrostatic guideways is generally ignoring the external load on the slider. A variation force also exists, caused by the different working positions, together with the dead load of the slider and that of other auxiliary devices. The effect of working position on vertical motion straightness is investigated based on the equivalent static model, considering the error averaging effort of pressured oil film in open hydrostatic guideways. Open hydrostatic guideways in LGF1000 are analyzed with this approach. The theoretical results show that the slider has maximum vertical motion straightness when the working position is closer the guiderail of Y axis. The vertical motion straightness reaches a minimum value as the working position is located at the center of the two guiderails on the Y axis. The difference between the maximum and minimum vertical motion straightness is 34.7%. The smaller vertical motion straightness is attributed to the smaller spacing of the two pads centers, along the Y direction. The experimental results show that the vertical motion straightness is 4.15 μm/1200 mm, when the working position is located in the middle of the Xbeam, and 5.08 pro/1200 mm, when the working position is approaching the Y guiderails, denoting an increase of 18.3%. The changing trends of the measured results validate the correctness of the theoretical model. The research work can be used to reveal the variation law of accuracy of the open hydrostatic guideways, under different working positions, to predict the machining precision, and provides the basis for an error compensation strategy for gantry type grinding machines.

HYDROSTATIC PRESSURE CALCULATION AND OPTIMIZATION FOR DESIGN OF BEAM & SLIDE-REST GUIDEWAYS IN HEAVY DUTY CNC VERTICAL TURNING MILL

Aiming at the approximate error of commonly used methods on calculation of hydrostatic pressures of closed hydrostatic guideways with multiple pockets, a more accurate solution is proposed. Taking design of beam ＆ slide-rest guideways for a heavy duty CNC vertical turning mill as an example, under an assumption that stiffnesses of guideways and their jointing structure are sufficiently large, the pressures of the pockets can be attained by adding a co-planarity equation that constrains pocket centers. Then, an optimization model is built to minimize the highest pocket pressure under additional constraints that are posed on the highest seal margin pressure, the highest levitating pressure of the pockets, and the maximum deformation of the guideways. The optimization problem is solved sequentially by using the methods of design of experiments and adaptive simulated annealing on iSIGHT software platform. The results show significant improvements to the original design. Optimized maximum hydrostatic pressure meets the requirement of hydraulic system.

STABILITY ANALYSES ON DYNAMIC CONTROL FOR A MOVING BODY LEVITATED MAGNETICALLY OVER ELASTIC GUIDEWAYS

Based on the Floquet theory on ordinary differential equationswith periodically variable coefficients and the bifurcation approachto nonlinear equations, a numerical approach to determining thestability region of control parameters is established for a dynamiccontrol system composed of a moving body levitated magnetically overflexible guideways. The system is nonlinearly coupled among theelastic deformation of guideways, disturbance the levitation positionof the body and electromagnet- ic control forces.

The Study of Contact Pressure Analyses and Prediction of Dynamic Fatigue Life for Linear Guideways System

The application of the linear guideways is very extensive, such as automation equipment, heavy-duty carry equipment, heavy-cut machining tool, CNC grinding machine, large-scale planning machine and machining center with the demand of high rigidity and heavy load. By means of the study of contact behavior between the roller/guideway and roller/slider, roller type linear guideways can improve the machining accuracy. The goal of this paper is to construct the fatigue life model of the linear guideway, with the help of the contact mechanics of rollers. In beginning, the analyses of the rigidity of a single roller compressed between guideway and slider was conducted. Then, the normal contact pressure of linear guideways was obtained by using the superposition method, and verified by the FEM software (ANSYS workbench). Finally, the bearing life theory proposed by Lundberg and Palmgren was used to describe the contact fatigue life.

An Analysis of Restricting Patterns of Aerostatic Guideways

The effects of restricting petterns of rectangular aerostatic guideway, restricitng orifce, spread of restricting orifices, size of air cavity and making tiny groove on the air foating surface etc, on the function of aerostatic guideway are analyzed by applying the method of finite element. This also provides a theoretical evidence for the design of rectangular guideways. The non-linear pressure equation set of finite element are sovled by using Newton metehod which guarantees quick and satisfactory convergence, high precision computation and wide range of applications.

Beijing No. 2 Machine-Tool Works

Established in 1953, the Beijing No. 2 Machine-Tool Works is a large state pillar enterprise producing precision and high-efficiency cylindrical grinders and NC cylindrical grinders, as well as processing centres, super-preci-sion processing machine tools, and special machine tools for auto manufacture. During the Eighth Five-Year Plan period, it was one of the top 500 enterprises in China’s machinery manufacturing, and enjoyed import and

Changjiang Machine-Tool Works

Situated in Yichang, Hubei Province, and established in 1969, the Changjiang Machine-Tool Works is a pillar enterprise in the machine tools industry of the Ministry of Machine-building Industry, and also China’s largest gear shaper producer. Through 28 years of continuous development, the works has developed from a special producer of gear shapers to a large state comprehensive enterprise, producing gear processing equipment, auto parts and accessories, agricultural machine, parts, metallurgical products, as well as environmental protection equipment and children’s toys. It has fixed assets of RMB

Shanghai Machine-Tool Factory Company Ltd.

A state-owned corporation, the Shanghai Machine-tool Factory Company Ltd. was founded in 1996, consisting of the Shanghai Machine-tool Factory, Shanghai No. 3 Machine-tool Factory, Shanghai No. 8 Machine-tool Factory and Shanghai Woodworking Machine Factory. Coveting an area of 360,000 square metres, the company has fixed assets valued at RMB440 million and a total of 1916 sets of equipment including

复合润滑结构改善滑动导轨表面爬行现象研究

滑动导轨在低速重载时产生爬行现象,严重影响机床的加工精度。为了改善滑动导轨的爬行现象,对滑动导轨表面复合润滑结构的设计和摩擦力分阶段表征进行了研究。在激光烧蚀微织构的基础上,采用高温高压镶嵌法制备了复合润滑微织构,基于摩擦试验,提出了摩擦力分阶段表征方法,探索了不同复合润滑结构对各阶段摩擦力特征参数的影响规律,建立了复合润滑结构改善爬行现象的理论模型,找到抑制爬行现象性能最优的复合润滑结构。研究结果表明:表面微织构仅影响摩擦力的严重黏滑和爬升阶段,而复合润滑结构对整个启动阶段都有显著影响。填充二硫化钼(MoS 2)的正弦沟槽与六边形凹坑组合的多级复合润滑结构(SF-3)改善表面接触状态和抑制爬行现象的效果最好。与光滑表面(SS)试样相比,SF-3试样爬行时间缩短了72%,第Ⅰ阶段失稳力减小了69.83%,第Ⅱ阶段和第Ⅲ阶段的摩擦突跃力分别减小了75.91%和80.17%。

常导高速磁浮轨道结构研发回顾与展望

轨道结构是常导高速磁浮交通系统中最重要的基础设施,也是系统建设成本的主要控制因素。通过分析常导高速磁浮轨道结构的系统特性,结合中国引进技术后的发展历程,将相关研究划分为德国原创试验、上海线建设、面向中长距离线路应用研发、维护与评估技术发展、面向更高速度研发等5个阶段,全面回顾20余年来轨道结构研发成果。在此基础上,系统阐述常导高速磁浮轨道结构的各类解决方案和工程实践经验,并提出下一步研究方向,可为我国发展时速600 km/h常导高速磁浮交通系统提供重要支持。

悬挂胶轮列车与钢桥的振动试验及仿真研究

为评价悬挂胶轮列车及钢轨道梁桥的结构性能,以开封悬挂式单轨示范线为背景开展现场试验与仿真研究。开发了胶轮列车-钢轨道梁桥耦合振动分析程序,根据现场实测的胶轮车辆的空气弹簧、走行轮刚度和阻尼等力学参数,建立胶轮列车模型。对车桥动力响应的现场试验与动力仿真分析结果进行综合比较,采用相关规范对列车走行性以及轨道梁桥的动力性能进行综合评估。结果表明:车桥动力特性及其振动响应的理论与实测结果基本吻合,车桥耦合分析方法可应用于悬挂式胶轮单轨交通系统振动性能研究;轨道梁竖向挠跨比小于相关规范的限值,竖向刚度设计合理;在列车竖向静活载作用下,相邻两跨轨道梁梁端竖、横向转角之和最大值分别为4.5‰和1.5‰;车速80 km/h下轨道梁纵、横向应力动力系数最大值分别为1.17和1.14;考虑到悬挂式胶轮列车没有脱轨风险,列车轮重减载率及钢轨道梁桥横向加速度较传统铁路偏大,其相应限值可较现行铁路规范适当放松。

基于磁流体轴承的大载荷磁流体二维导轨平台研究

在现有的精密机床中,空气静压导轨平台存在阻尼突变、载荷不高的问题,基于磁流体轴承,提出了一种大载荷磁流体二维导轨平台。首先,对基于磁流体的导轨平台关键问题进行了研究,包括空气损耗问题和磁流体尾迹问题;然后,采用磁流体压力轴承设计了一个双U形导轨平台结构,并将顶部、底部和侧部轴承垫紧密地放置在一起,从而在动子上形成了一个储液层;采用上下磁化配置的导轨平台具有6个轴承垫,每个轴承垫由多个小型磁体组成;其次,对载荷能力、刚度和涡流阻尼进行了数值模拟;最后,选用了煤油基磁液、铝材和铁素体不锈钢制备了一台平台样机,进行了平台的性能测试,对该导轨平台的有效性进行了验证。研究结果表明:该平台的平面度为±7μm,具有较高的可重复性,明显优于现有基于磁流体轴承的精密运动系统;在相同行程和尺寸条件下,与气动平台相比,该平台的最大有效载荷为140 N,提高了40%;阻尼在2 N·s/m至4 N·s/m之间相对恒定,且可预测,解决了气动平台的阻尼突变问题,有利于实现导轨平台高精度定位的目的。

音圈电机直驱气浮升降平台的设计及其性能测试

在半导体的精密加工与精密测量中,针对一些光路限制、加工设备固定的情况下,设计了一种音圈电机直驱的气浮升降平台,承载起工件进行精密定位。平台的驱动元件采用两个高精度、高频率、无摩擦的音圈电机进行驱动,平衡元件采用了低摩擦气浮气缸进行平衡运动部件的重力,导向元件采用了多孔式节流的环绕式气体静压导轨进行导向,同时反馈元件采用高精度光栅尺作为实时反馈装置。对气体静压导轨进行了气体理论分析,用Ansys仿真软件进行导轨承载力和刚度的仿真,并结合实验进行验证仿真分析。考虑到两个音圈电机驱动时的机械耦合作用,采用了主令并行交叉耦合控制算法,来对升降平台进行精密控制。最后对升降平台的定位精度、俯仰误差、偏摆误差、直线度进行了性能测试,证明了该升降平台具备了精密加工与精密测量的能力。

导轨式胶轮车辆传动轴失效原因分析与优化设计

[目的]导轨式胶轮车辆传动轴的结构可靠性对列车运行安全性至关重要。该车辆在某条城市轨道交通线路上进行冰雪试验时,多次出现传动轴断裂现象而导致失效。因此需分析传动轴失效原因,并对其进行优化设计。[方法]从传动轴失效断面宏观检测及失效件材料理化检测两方面分析了传动轴断裂的原因。采用无线扭矩测试系统对该条线路五号站—六号站、五号站—七号站区间传动轴的实时载荷进行了测试,并分析其测试结果。优化了传动轴结构设计。对优化后的传动轴台架进行了强度测试,以及对优化后的传动轴进行了疲劳试验。[结果及结论]传动轴断裂的原因为:十字轴的过载脆性断裂和双联轴套的疲劳断裂。两个区间的测试结果显示:传动轴的最大扭矩均出现在车辆打滑状态下,其实际扭矩虽小于设计的最大工作扭矩,但由于扭矩短时间内发生变化时,其受到的冲击能量远大于正常工况下的扭矩变化值。传动轴结构的优化措施为:增大十字轴的轴径,在十字轴圆弧过渡处增大倒圆角,进一步减小应力集中;通过在双联轴套上增加加强筋,提高双联轴套轴肩部的强度。优化后的传动轴台架强度测试表明,满足设计要求;优化后的传动轴疲劳试验表明,试验合格。

中速磁浮列车-轨道梁-桥墩横向耦合振动分析

为研究桥墩参与作用的中速磁浮横向耦合振动,基于车辆动力学、结构动力学和PD控制算法原理,建立了考虑桥墩参与振动的车-桥横向动力分析模型。基于Mathematica编写的仿真程序分析了中速磁浮系统横向耦合振动的动力响应,研究了桥墩高度变化对系统振动的影响规律。研究结果表明,风荷载是中速磁浮系统横向耦合振动的主要激振源;是否考虑桥墩受风荷载作用对车辆系统动力响应的影响有限,桥墩高度变化对车辆系统的动力响应影响较小;是否考虑桥墩受风荷载作用对轨道梁位移响应的影响较大,差异值可达20%,桥墩高度与轨道梁位移不是单一线性关系,存在一个临界桥墩高度值,小于临界值时桥墩高度与轨道梁位移呈正相关,大于临界值时呈负相关。

Halbach型磁浮列车永磁轨道的空间磁场计算模型

Halbach阵列因其显著的单边聚磁特性,成为提升永磁轨道悬浮性能的重要途径。针对Halbach型永磁轨道复杂的空间磁场分布行为,提出一种简捷高效的三维磁场分析方法。首先在均匀磁化假设的前提下,建立基于毕奥-萨伐尔定律的单块永磁体的解析模型。然后基于磁通叠加得到完整轨道的三维磁场解析模型。最后通过对实测值、解析解和有限元解的对比分析,验证所提模型的可靠性和准确性。本研究结果可为永磁轨道的进一步设计和优化提供重要的参考依据。

微织构对V型滑动导轨副摩擦磨损特性影响的研究

V型滑动导轨副具有低成本、良好的承载能力和导向性等优点,至今仍应用于很多机械设备中,但同时也存在着摩擦系数大、易磨损和低速稳定性差等缺点。为提高V型滑动导轨副的摩擦学性能,利用激光表面织构化技术分别在导轨的接触面上设计并制备直线和椭圆微织构。通过不同仿真软件对激光制备出的微织构是否产生流体动压效应进行验证,分析微织构对导轨接触面的接触应力的影响。利用自制往复滑动导轨试验平台在混合润滑条件下测试了不同类型织构化导轨副的摩擦磨损性能。结果表明,织构化导轨副均可以产生流体动压效应,且椭圆微织构可以产生更大的流体动压效应。此外,椭圆微织构仅位于下导轨表面可以较大程度降低其接触应力。因此,当椭圆微织构位于下导轨表面时减摩效果最好,具有最低的平均摩擦系数,与无织构导轨副相比下降了31.7%。

高速发射装置柔性传动系统非线性运动研究

为满足高速发射装置的使用要求,针对弹链非线性运动导轨进行设计分析和优化,以确保弹体顺利传送至击发位置。导轨的设计优化是确保高射速、高精度发射系统供弹连续性和可靠性的关键。通过建立高速发射装置导轨曲线方程,并分析导轨不同位置的曲线特性,针对其设计中存在的柔性冲击,运用样条插值对导轨曲线进行优化设计,并对优化后的导轨进行仿真验证,验证结果满足发射装置的使用要求。文中旨在为改善发射装置非线性运动导轨动力学特性和提高导轨使用寿命提供理论依据。

龙门加工中心横梁导轨靠合面变形分析与补偿研究

横梁自重及其他功能部件重量等多源因素共同造成了横梁导轨靠合面的Z向凹陷及扭转变形现象,进而导致靠合面精度失真并影响龙门加工中心横梁Y向综合直线度。为消除不利因素对导轨靠合面产生的影响,文章基于有限元分析法,聚焦横梁上下两导轨靠合面,建立仿真分析试验方案,求解不同位置处变形量并拟合绘制出其全程变形曲线,依据该曲线对导轨靠合面进行形变量修复补偿。实际测量结果表明:补偿后的龙门加工中心横梁Y向综合直线度精度得到有效提升。

齿条导轨组件安装精度的调校方法

齿条导轨组件安装精度要求高,调校方式主要依靠经验,调整螺钉拧紧力矩与导轨位移关系尚不明确,故对齿条导轨组件开展安装精度调校方法研究,探索调整螺钉拧紧力矩与导轨位移关系,提高装配精度,保证产品质量。基于奇异函数建立了调整螺钉拧紧力矩与导轨位移关系,采用遗传算法对特定位置螺钉拧紧力矩进行优化求解,形成了一种齿条导轨组件直线度与平行度调校方法,并通过有限元仿真验证了该调校方法的可行性。结果表明,该方法能够根据导轨偏移量求解相应位置的调整螺钉力矩,减小导轨调校的盲目性,降低导轨安装的直线度和平行度误差,提高直线导轨的安装精度。