数控机床主轴轴承失效分析

某数控机床主轴轴承运行613 h后出现振动异常,发现失效轴承个别钢球表面存在明显损伤痕迹,通过宏微观观察,化学成分分析,能谱分析等方法对钢球表面的损伤痕迹进行研究。结果表明,由于金属异物颗粒进入轴承,异物与钢球发生粘着磨损,随着粘着磨损作用加剧,在钢球表面产生“白层”,“白层”内部萌生接触疲劳裂纹,疲劳裂纹扩展使钢球表面剥落,形成剥落坑,引起轴承失效。失效轴承的各部件硬度差值超出标准,加速了轴承的失效。因此建议对轴承添加防尘盖或密封圈,提高润滑油脂的洁净度,避免外界异物污染轴承引起失效,并在实际生产中加强轴承材料的质量控制。     

Strain field analysis and sensor design for monitoring machine tool spindle bearing force

The fluctuating strain field produced by the rolling motion of the spindle bearing is analyzed by an elastic model and verified with experimental data. This strain field analysis is of considerable practical significance because of its close correlation to spindle bearing preload, cutting forces, and bearing running conditions. Based on the model, a conventional sensing scheme with strain gages mounted in a groove ground around the bearing outer ring is optimized by selecting proper sensor sizes, locations, and configurations such that signal cross-over error is minimized. In addition, the feasibility of a non-invasive sensing scheme achieved by attaching high sensitivity sensors on the outside surface of the spindle housing is studied. From the strain model, it is found that the level of strain field at the housing surface is substantially lower, and its distribution is not concentrated. Therefore, high sensitivity sensors and different sensing schemes are needed. Simulation results show that, compared with the conventional scheme, the output of this scheme requires less signal processing when the force acting on the bearing is fluctuating.     

机床主轴电机的选择研究

电主轴是机床的核心部件,本文就主轴电机的选择,从使用要求、控制要求和经济性要求等方面对各类电机进行了分析比较,结合相应调速系统的对比,选择出适合机床主轴用执行电机的类型和调速系统。     

磁浮磨床主轴的电磁轴承的阻尼特性

利用安装于磨床主轴上的电磁轴承的阻尼特性，应用最优控制理论，使主轴在外界激扰下，其响应在短时间内迅速衰减，从而提高了转子的抗失稳、抗干扰能力，保证了磨床的磨削精度。经过仿真计算，其控制效果满足要求。     

Programming spindle speed variation for machine tool chatter suppression

This paper presents a novel method for programming spindle speed variation for machine tool chatter suppression. This method is based on varying the spindle speed for minimum energy input by the cutting process. The work done by the cutting force during sinusoidal spindle speed variation S³V is solved numerically over a wide range of spindle speeds to study the effect of S³V on stable and unstable systems and to generate charts by which the optimum S³V amplitude ratio can be selected. For on-line application, a simple criterion for computing the optimal S³V amplitude ratio is presented. Also, a heuristic criterion for selecting the frequency of the forcing speed signal is developed so that the resulting signal ensures fast stabilization of the machining process. The proposed criteria are suitable for on-line chatter suppression, since they only require knowledge of the chatter frequency and spindle speed. The effectiveness of the developed S³V programming method is verified experimentally.     

机床主轴结构参数优化设计

以机床主轴为优化设计对象,将优化设计思想与Matlab相结合,利用外惩罚函数法对机床主轴进行建模优化,求解出参数并用分支定界法确定主轴参数。然后运用ANSYS对其进行模态分析,分析了主轴的前6阶固有频率、振型和临界转速,验证了机床主轴结构优化设计的合理性,为机床主轴的结构优化设计提供参考和依据。     

轴承印字机的PLC全自动化控制

提出一种新型轴承印字方法。结合轴承印字流水线的具体要求，详细介绍了以OMRON PLC为主控制器的系统硬件配置、软件结构和实现过程。     

机床主轴、进给电动机控制线路的设计

本文阐述了用继电接触器及PLC控制机床主轴、进给电动机控制线路的设计方法和思路.本程序适合于三菱系列的PLC.     

机床主轴的PLC直流伺服系统

利用可编程控制器(PLC)控制系统的高可靠性、编程及维护方便、体积小的特点，将其应用于环流可逆调速系统中，研制出基于PLC的机床主轴直流伺服系统，使机床主轴的伺服控制更加简单、可靠和稳定。     

数控机床主轴准停控制及应用

采用数控系统完成主轴准停控制是现代数控机床实现高精度主轴准停的常用方式；同时能够满足加工中心自动换刀及镗削加工工艺的需要。     

机床主轴智能磨削工艺软件的研究与开发

以机床主轴磨削工艺方案智能推理为研究对象,研发了满足智能化制造机床主轴的磨削工艺软件。该软件汇集了机床主轴智能磨削工艺基础数据库、工艺知识库、工艺实例优选与智能推理、数控自动编程等多个模块,并应用于数控外圆磨床生产实践中。结果表明:该磨削工艺软件能显著提高主轴数控磨削工艺方案决策的准确度,决策正确率达到96%,工艺决策时间缩短约50%,从而提高加工效率。      

机床电主轴的单片机矢量控制

应用单片机80C196KC为控制核心，设计了机床电主轴的矢量控制系统，简化系统结构，提高系统的动静态性能。     

Simulation of thermal behavior of a CNC machine tool spindle

The thermal deformations of a CNC machine tool spindle are the major contributor of thermal error. It is very significant both theoretically and practically to study how to accurately simulate the thermal error of the spindle. Firstly, this paper proposes a method for computing the coefficient of convection heat transfer of the spindle surface by referencing the theory on computing the coefficient of convection heat transfer of a flat plate when air flows along it. Secondly, the temperature field and thermal errors of the spindle are dynamically simulated under the actions of thermal loads using the finite element method. Thirdly, the characteristics of heat flow and thermal deformation within the spindle are analyzed according to the simulation results. Fourthly, the selection principle of thermal key points, which are indispensable for building a robust thermal error model, is provided based on the thermal error sensitivity technology. At last, a verification experiment is implemented on a CNC turning center, and the results show the simulation results are satisfying to replace the experiment results for further studies.     

机床主轴回转精度计算机辅助测试系统

文章构建了机床主轴回转精度计算机辅助测试系统.该系统较传统测量系统具有测量精度高、在线与实时测量、数据处理能力强、操作方便等特点.     

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.     

An improved thermal model for machine tool bearings

Thermal model for machine tool spindle is of great importance to machine tool design. Traditionally, the thermal contact resistance between solid joints and the change of the heat generation power with the bearing temperature are often ignored when thermal characteristics of a machine tool spindle are analyzed. This has caused inaccuracies in the thermal model. With the heat source models and the heat transfer models from Bossmanns and Tu [Journal of Manufacturing Science and Engineering 123 (2001) 495–501, International Journal of Machine Tools & Manufacture 39 (1995) 1345–1366], a model including the thermal contact resistance at solid joints based on a fractal model and the change of the heat generation power, viz. the amount of the heat generation per second, with the bearing temperature increases is developed. The complete thermal model is used to simulate the temperature distribution in grinding machine housing with a conventional spindle bearing. Compared with experiment, it is shown that the completed model is much more accurate than the traditional model which ignores the two important factors above. The thermal expansion of the housing system is analyzed.     

Digitally controlled output filters for improvement of temperature behavior of machine tool main spindle drives

Variable speed main spindle drives of machine tools are usually fed by three-phase two-level inverters. Because of the switching operating mode of these inverters, the motor voltages and currents contain harmonics which do not contribute to torque formation but solely to an undesirable warming of motor spindle elements. This warming results in thermal elongation of the spindle shaft and therefore to a deviation in dimensional accuracy. The increased wear of the spindle bearings through high temperature differences between the inner and outer rings of the bearings is another drawback. This paper proposes a novel high-performance control system of an interior permanent magnet synchronous motor (IPMSM) using an inverter with an LC output filter. The combination of inverter and filter reduces the motor losses by compensating the switching ripples and therefore leads to an evident improvement of the temperature behavior of the main spindle drive.     

Modeling of dynamic characteristic of the aerostatic bearing spindle in an ultra-precision fly cutting machine

Axis orientation stability of aerostatic bearing spindles has great influence on machining precision of ultra-precision fly cutting machines used for processing ultra-precision optical components of large diameter. Mid-spatial frequency errors (amplitude<0.1 μm, wavelength about 100 nm) always existed on the machined surfaces along feeding direction. Generally, the waviness errors on processed surfaces will impact the performance of workpiece used as optical components greatly, and the tilting motions of spindles were believed to be the main source which produced the waviness errors. In this paper, to study the tilting motions of spindles, the Euler dynamic equations of angular displacements of spindles were proposed, and analytic solutions of the equations were also presented. At the same time, the 3D surface profile simulations of workpieces based on analytic solutions of Euler equations were achieved. The simulation results have been verified by lots of experiments on an ultra-precision fly cutting machine. At last, the inertia tensor criterion which can decrease the waviness errors of machining surface was represented, and it can be applied to instruct the structure design of aerostatic bearing spindles.     

Sensitivity analysis of the 3-PRS parallel kinematic spindle platform of a serial-parallel machine tool

The special configuration of a serial-parallel type machine tool possesses five degrees of freedom and provides more flexibility in NC machining. The parallel spindle platform plays the key role in manipulating three directions of movement. In this study, the inverse kinematics analysis of the platform is derived first. A sensitivity model of the spindle platform subject to the structure parameters is then proposed and analyzed. All the parameters influencing the position and orientation of the spindle platform are discussed based on the sensitivity model and the simulated examples. Critical parameters to the accuracy of the cutter location can then be found, which are the slider position, the strut length, and the tool length.