Thermal characteristics of the spindle bearing system with a gear located on the bearing span

High cutting speeds and feeds are essential requirements of a machine tool structure to accomplish its basic function which is to produce a workpiece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since bearings in high speed spindle units are the main heat source of total cutting system, in this work, the thermal characteristics of the spindle bearing system with a tilting axis were investigated using finite element method to improve the performance of the spindle bearing system. Based on the numerical results, a specially designed prototype spindle bearing system was manufactured. Using the manufactured spindle bearing system, the thermal characteristics were measured and compared to the numerical results. From the comparison of the numerical results with the experimental results, it was found that the finite element method predicted well the thermal characteristics of the spindle bearing system.     

An elastic deformation model of high speed spindles built into ball bearings

Kinematic characteristics and elastic deformation properties of ball bearings such as stiffness, axial, and radial deflections of the rings, speeds of balls, contact angles, and loads, all vary strongly with rotational speed, temperature, and axial preload. This paper presents an elastic deformation model of spindle units built into ball bearings, which are running on high rotational speed and axial preload. For this, software for simulation of the high speed spindle units was developed and introduced into a practical use. A computer aided analysis of the model was carried out and experiments were made, which showed a significant effect of high rotational speed, cutting load, bearing axial preload, and a new effect for which the criteria for a choice of bearing preload are given.     

Trends in the P/M hard metal industry

The intention of this paper is to give an overview of selected R&D trends in the cemented carbide field, focusing on work performed in recent years. Due to the large activity in the field, it is not feasible to give a comprehensive review of all research activities in the hard metal industry and academia. Therefore, focus has been given to areas with a large number of publications in journals on the field of cemented carbides, cermets and powder metallurgy of hard materials, which indicates interesting emerging areas, techniques and trends. Such areas include fine grained materials, interfaces, alternative binders, alternative sintering techniques, and gradients; high resolution microscopy and electron backscatter diffraction. Amongst emerging trends, coupling between experiments and modelling at different scales is growing, as well as three dimensional modelling of microstructure evolution. Trends are discussed and an outlook for future development in the respective fields is given.     

Compensation of thermo-dependent machine tool deformations due to spindle load: investigation of the optimal transfer function in consideration of rough machining

The thermal behavior of a machine tool is an important indicator for the grade of production accuracy and indirectly for the market success. The load-dependent temperature distribution and the resulting deformation of the machine tool are influenced by a variety of design and thermo-technical parameters. The main spindle of a machine tool is, without any doubt, the major heat source within the machine structure. The object of the scientific investigation presented in this article is the development of an approach to robust compensation of thermo-dependent machine tool deformations due to spindle load in consideration of rough machining. The focus of the work concentrates on the identification of the model with the highest compensation performance. The underlying concept for the compensation of thermo-dependent machine tool deformations is the indirect approach by using the speed and the effective power of the main spindle for the calculation of the Tool Center Point (TCP) displacement. The presented modeling approach requires the knowledge of the TCP displacement in X-, Y- and Z-direction depending on the speed and the effective power of the main spindle. As a tool for modeling the thermo-dependent behavior of a milling machine, a load test rig for repeatable, defined long-term loading of the main spindle has been developed. It simulates the cutting force depending on the spindle speed and the torque and applies load to the main spindle. The spindle speed and the spindle effective power can be taken directly from the numerical control of the machine tool. An important advantage of the presented compensation method is the fact that it does not require any external sensors. The displacement of the TCP has to be measured, but only during modeling. The relationship between the speed/power of the main spindle as a cause and the displacement of the TCP in X-, Y- and Z-direction as an effect can be determined by a transfer function. This paper compares the compensation results depending on the transfer function and identifies the model with the best compensation performance. The validation of the compensation method is executed by using the example of two different speed and power spectra of the main spindle.     

数控高速电主轴技术及其发展趋势

高速加工是近年来发展起来的先进制造技术，电主轴是实现机床高速化的核心部件。本文详细阐述了高速主轴的技术难点、存在问题、发展现状，并提出了我国电主轴技术发展方向。     

Ultra-high-speed grinding spindle characteristics upon using oil/air mist lubrication

Grinding efficiency measured in terms of material removal rate is achieved by employing ultra high wheel speeds. The spindle is a key component for ultra-high-speed grinding machine tools and the development of a “high power–high rotational speed” spindle is a daunting task owing to the lubrication challenges. The oil/air mist lubrication system with an effective heat dissipation method simplifies the spindle configuration. This paper emphasizes two main issues: (1) the development of an oil/air mist lubricated ultra-high-speed grinding spindle and (2) the grinding performance of such a spindle for hard and tough materials.     

Metal Dusting Protective Coatings. A Literature Review

Metal dusting is a catastrophic form of carburization attack that takes place in carbon-supersaturated gaseous atmospheres, and is most commonly encountered in steam reforming processes such as the production of hydrogen or syngas for ammonia, Fischer?CTropsch and methanol applications. The consequence of metal dusting can be a severe loss of metal from the process units, leading to high-cost maintenance and serious safety issues. The present literature review discusses the latest developments within metal dusting protection of alloys with special emphasis on protective coatings. In the first part of the paper, an overview of the main theories for metal dusting of alloys as well as fundamental studies is provided. In the second part, the paper focuses on the different methods to prevent metal dusting, including surface poisoning, alloying, chemical, mechanical and laser treatments as well as coatings. Particular focus is given to coatings and their composition, and fabrication methods, and a critical analysis of the different materials?? behaviours and the suitability perspectives of deposition techniques are provided.     

孔内环形槽加工装置

用本孔内环形槽加工装置加工小孔、深孔内的多条环形沟槽,克服了以往使用偏心刀杆存在的不足,加工后的环形沟槽完全能够达到图纸设计要求,并且生产效率高.     

Z5132节点球加工中心主轴系统的参数及控制

本文针对节点球加工中心主传动系统的调速范围、输出扭矩及主轴定向控制问题，通过主传动系统的功率特性分析，得出主轴功扭特性曲线图并给出了主轴变速范围。主轴驱动控制单元采用SPWM控制方式，主轴准停采用磁力定向方式，满足了不同规格节点球加工对主轴系统的要求。     

机械故障诊断技术趋向分析

简要地介绍了机械诊断技术的发展概况，阐述了其应用现状及目前存在的主要问题，分析了其发展趋势向。     

A review on spindle thermal error compensation in machine tools

Thermal error caused by the thermal deformation is one of the most significant factors influencing the accuracy of the machine tool. Among all the heat sources which lead to the thermal distortions, the spindle is the main one. This paper presents an overview of the research about the compensation of the spindle thermal error. Thermal error compensation is considered as a more convenient, effective and cost-efficient way to reduce the thermal error compared with other thermal error control and reduction methods. Based on the analytical calculation, numerical analysis and experimental tests of the spindle thermal error, the thermal error models are established and then applied for implementing the thermal error compensation. Different kinds of methods adopted in testing, modeling and compensating are listed and discussed. In addition, because the thermal key points are vital to the temperature testing, thermal error modeling, and even influence the effectiveness of compensation, various approaches of selecting thermal key points are introduced as well. This paper aims to give a basic introduction of the whole process of the spindle thermal error compensation and presents a summary of methods applied on different topics of it.     

空气静压主轴有限元建模及动态特性研究

为提高空气静压轴承支撑的空气静压主轴的动态工作性能,文章利用Fluent计算出了空气静压轴承在不同供气压力下气膜刚度,利用Ansys Workbench中的轴承单元和弹簧—阻尼单元模拟轴承支承,对主轴系统进行了模态分析和动态响应分析,得到不同供气压力下主轴系统的固有频率、振型以及激振力作用下的位移幅频动态响应曲线。结果表明,随着供气压力的增加,轴承气膜刚度增加,且对主轴系统的低阶模态和高阶模态影响不同。另外随着气膜刚度增加,谐振频率逐渐增大、振幅减小,系统抵抗受迫振动能力逐渐增强。研究结果为提高空气静压主轴的动态性能提供了一定的理论依据。     

Evaluation of an internally spring preloaded four contact-points bearing for spindle units

In this paper, the concept of an internally spring preloaded four contact-points bearing for the use in high precision and high speed applications is investigated. It is designed as a compact self-contained fixed bearing unit that is free of play, easy to mount and resistant against temperature differences between the inner and outer ring. The concept of the bearing, its functionality and properties are introduced and the results of an experimental analysis of a first prototype are presented. The prototype bearing, which is based on a hybrid 7014 spindle bearing with an additional spring preload unit, was manufactured by hard turning. Its properties are compared to those of similar two and three contact-points spindle bearings. Typical requirements in modern high precision applications, e.g. machine tool spindle units, and limiting characteristics of bearings, such as displacement, stiffness, friction torque and operating temperature, are considered. Finally, the potential of the new bearing concept is discussed.     

高速电主轴单元的热-结构性能虚拟仿真分析

主轴单元的热变形是高速加工中影响精度的主要因素。本文利用大型有限元分析软件ANSYS对高速电主轴进行了热-结构耦合分析。计算结果显示，设计的高速电主轴单元主轴轴承、主轴前端温升理想，工作端轴向热位移很小。这表明设计的电主轴具有良好的热-结构性能，可以满足加工精度要求。     

立式加工中心主轴系统热变形试验及误差补偿

立式加工中心经过长时间的运行之后,主轴箱及主轴系统组成的单元会产生热变形,这影响到被加工零件轴向尺寸的加工精度。以VMC750立式加工中心为试验对象,测量主轴箱多点温度及主轴变形伸长量,确定主轴变形的主要原因,建立误差补偿模型,通过对立式加工中心加工过程中的热误差进行了实时补偿实验,结果表明：通过热变形补偿,主轴系统热变形实测为0.28～0.33 mm,其误差可减少75％左右,验证了该模型的有效性。     

数控机床电主轴单元热-结构特性动态分析

分析了高速电主轴单元热变形机理与散热机制,对主轴单元热态特性要求进行了描述,利用AN-SYS对高速电主轴进行了热-结构耦合分析。通过改变电主轴有限元模型中的边界条件,对不同转速、润滑方式、冷却结构设计、内装式电机选择条件下电主轴热-结构特性进行了对比分析。根据分析结果,提出了改善电主轴热态特性的措施,为电主轴冷却结构设计提供了参考。     

声发射技术在大型观览车主轴检测中的应用

主轴是大型观览车结构中的重要部件,具有难以拆卸的特点,一旦发生故障,危险性极大。根据大型观览车主轴的结构特点,制定了相应的声发射检测方案,对在役观览车主轴中的异常声响进行了声发射在线检测,分析并给出了异常声响信号的声发射参数特征、定位特征和波形频谱特征,并对两个检验周期中声发射检测的结果进行了比较。结果表明,声发射检测技术可以用于大型观览车主轴运行状态的监测与评价。     

加工中心主轴部件及其主轴箱的热特性有限元分析

现代机械工业对机床精度提出了越来越高的要求.机床主轴部件和主轴箱的热特性是影响机床精度的主要因素之一.文章建立了加工中心主轴部件及其主轴箱的温度场模型并进行了数字模拟仿真.首先预测了机床主轴部件的热平衡时间能,并以温度曲线的形式表示出来,然后计算出主轴部件和主轴箱的热变形.依据这些我们能够得到主轴的轴向和径向误差,为主轴部件的设计计算奠定了基础.     

Magnetic materials for EAS sensors

An overview is given of the new technology of electronic article surveillance (EAS). The focus is on the magnetic materials used principally as sensors in EAS. The principal characteristics of these materials that make them suitable as tags are highly nonlinear B-H characteristics or strong magnetomechanical coupling with low acoustic loss. Specific materials characteristics are described for various EAS systems.     

影响高频电主轴工作寿命的主要原因及解决方法

对高频电主轴的发热和损耗状况进行了分析，针对影响电主轴．寿命的主要原因，提出了提高电主轴转子加工精度的措施和选择合理的电磁方案以降低温升；阐明了电主轴轴承结构的合理选择覆润滑方式。