高速加工中心7:24主轴/刀柄联接的可行性分析

在高速数控机床加工中,由于高速旋转中的离心力作用,传统7:24主轴/刀柄联接的径向位移与两者间的间隙随转速的提高呈平方关系增长。径向间隙的存在导致定位精度和重复定位精度不高、轴向和径向刚度低等问题,严重影响加工精度和质量。论文采用有限元分析方法,验证了主轴转速为15000r/min时,加工中心采用7:24主轴/刀柄联接的可行性。并提出改进7:24主轴/刀柄联接性能的方法。     

高速加工中心7∶24主轴/刀柄联接的可行性分析

在高速数控机床加工中,由于高速旋转中的离心力作用,传统7∶24主轴/刀柄联接的径向位移与两者间的间隙随转速的提高呈平方关系增长.径向间隙的存在导致定位精度和重复定位精度不高、轴向和径向刚度低等问题,严重影响加工精度和质量.论文采用有限元分析方法,验证了主轴转速为15000r/min时,加工中心采用7:24主轴/刀柄联接的可行性.并提出改进7:24主轴/刀柄联接性能的方法.     

主轴-刀柄和刀柄-刀具结合面参数对稳定性Lobe图的影响

为探索主轴-刀柄和刀柄-刀具结合面参数与立铣加工过程稳定性的关系,以主轴-刀柄和刀柄-刀具结合面参数辨识方法和两自由度立铣加工过程动力学模型为基础,研究了主轴-刀柄,以及刀柄-刀具结合面参数等因素对稳定性Lobe图的影响。结果表明:主轴-刀柄和刀柄-刀具结合面的直线刚度对稳定性Lobe图的影响最大,其他结合面参数对稳定性Lobe图均有不同程度的影响;和主轴-刀柄结合面参数相比,刀柄-刀具结合面参数尤其是转动刚度对稳定性Lobe图的影响更大。     

数控机床7：24锥度刀柄主轴连接性能的有限元分析

数控机床刀柄/主轴连接性能直接影响数控加工的位置、精度和安全性,文中采用弹塑性力学理论和有限元方法,研究数控机床7:24锥度刀柄/主轴连接在高速切削加工中引起的性能变化,分析了轴向拉力、旋转速度等参数对其连接性能的影响,并提出了改进方法.     

加工中心主轴部件刚度分析

高速加工是一项十分重要的先进制造技术,为了实现高速加工,首先必须有高质量的加工中心.主轴部件是加工中心的核心部件,其刚度特性在很大程度上决定了高速加工中心的加工质量,也是影响其加工精度的重要因素.文章利用Pro/Engineer软件建立主轴单元虚拟样机模型,完成了主轴单元虚拟样机模型之后,通过Pro/Engineer与ANSYS的软件接口将Pro/Engineer中主轴零件的模型转换成ANSYS中的有限元模型,进行主轴的刚度分析,找出了危险截面,验证了主轴单元设计方案的合理性.     

高速切削加工时标准7∶24锥度刀柄及HSK刀柄的分析

将机床主轴与刀具相联结的刀柄是影响加工精度、机床和刀具磨损及加工效率的关键部件。针对高速切削对刀柄的要求,对标准7∶24锥度刀柄及HSK空心短锥刀柄的特点及性能进行对比和分析,给出各自的适用场合和切削条件。同时指出HSK空心短锥刀柄虽具有突出的优点,但并不能完全取代7∶24锥度刀柄,应根据具体情况选用才能收到良好效果。     

基于主轴轴承运行刚度的高速主轴动力学建模

高速主轴是高速加工关键功能部件之一,其动力学性能对机床加工质量有着重要的影响。基于赫兹接触理论计算了主轴轴承动态运行刚度并构建了主轴轴承的刚度矩阵;基于Timoshenko梁理论获得高速旋转梁单元运动方程;基于主轴轴承单元、梁单元与盘单元构建了某高速主轴系统有限元模型,并进行了静动态实验测试。结果表明:所建立的动力学模型是准确的,为主轴系统结构优化提供了理论指导。     

用于硬铣削的Excelerator立铣刀

Greenleaf公司的Excelemtor小直径立铣刀是为高效铣削难加工材料而设计开发的。该刀具采用Greenleaf公司先进的可转位陶瓷刀片，刀体、刀柄和刀片夹紧机构的设计使其可在40000r／min或更高的主轴转速下进行高速加工。     

基于均布弹簧模型的电主轴有限元建模及动态特性分析

为了研究轴承刚度、结合面刚度等各个参数对电主轴动态特性的影响、验证弹簧模型在电主轴建模中的适用性,基于国产电主轴170XDS20Z11,使用有限元方法,利用Ansys workbench对电主轴单元进行建模。首先分别建立刀具、刀柄和主轴的模型,结合实验进行动静态特性的分析与验证;然后基于均布弹簧的模型对刀柄—刀具结合面、刀柄—主轴结合面和轴承进行建模,通过对实验数据的拟合得到了结合面弹簧的刚度数值,通过预测刀尖点频响函数的方法验证该模型的准确性。研究得出了轴承刚度和结合面刚度的最佳范围,证明了弹簧模型的准确性和实用性。     

自动换刀偏摆检测系统

在配有自动换刀装置的机床上进行加工时，其切屑会咬进刀柄和主轴之间而影响加工精度，特别是使用高速化的ATC(Automatic Tool Changer自动换刀装置)和以KM、HSK为代表的两面定位夹紧刀柄时，咬人切屑的概率更高。     

Evaluation of the stiffness chain on the deflection of end-mills under cutting forces

This study presents the investigation of the stiffness of the system formed by the machine-tool, shank and toolholder, collet and tool. Cutting forces induce the deflection of the system, and consequently an error appears on the machined surface.Comparing values obtained from cantilever beam models applied to the cutting tool, analytical or FEM, with those experimentally obtained, large differences have been observed, which in some cases are more than 50%. For this reason, we have proceeded to evaluate the stiffness of each of the existing elements between the machine bed and the tool tip. Thus, deflections of the machine-tool, toolholder and toolholder clamping in the spindle, tool clamping in the toolholder, and tool itself, were measured experimentally under the effects of known forces.The final application is the ball-end milling of complex surfaces, an operation commonly performed in the finishing of moulds or forging dies, where errors of more than 70 μm are not unusual. A great part of this error comes from the deflection of the machine-tool assembly, spindle, shank and tool, due to the high cutting forces of the high speed machining of tempered steels. Cutting forces can be estimated using a semi-empirical approach, and from here some values of probable errors may be taken into account to check if the CNC programs are sufficiently adapted. However, a previous study of the deflection chain in the cutting process is needed, as is presented in this work.Results show that stiffness of the slender and flexible tools is 15 times lower than that of the machine and toolholder system. But this correlation is only 5–7 times lower for shorter and thicker tools.     

对高速电主轴静刚度的测试及分析

为研究高速电主轴静刚度的特性,利用DH3818静态应变测试仪,以高速电主轴为本体,研究高速电主轴静刚度与作用在电主轴上的力之间的关系。使用静态应变测试仪和力传感器在电主轴处于稳定状态时对1.5×10~4r/min电主轴和6×10~4r/min电主轴的径向刚度和轴向刚度进行测试,通过测试得知:高速电主轴静刚度大小与端部变形量成反比。对比分析1.5×10~4r/min电主轴轴向刚度与径向刚度,可知电主轴径向刚度远远大于轴向刚度;对比分析1.5×10~4r/min与6×10~4r/min电主轴径向刚度,可知最高转速低的电主轴比最高转速高的电主轴刚度大。又因为过低的静刚度会对数控机床的性能造成影响,所以提高电主轴静刚度也可使机床的性能得到提高。     

Controlling toolholder fretting through simple design modifications

During machining, cutting forces exerted on a toolholder may cause its shank to deflect and impact on the spindle pocket surface. This repetitive impact between the spindle and toolholder may result in a fretting condition. Over time, this fretting condition leads to wear and corrosion damage that is costly to repair and can potentially affect machining performance. Since fretting conditions are caused by vibrations and different toolholder designs will have different dynamic characteristics, it is possible to find those designs that would minimise shank deflections, and thus minimise the fretting condition. In this paper, through finite element simulations and experimental testing, two types of toolholders were studied: straight shank and tapered shank. It was found that within typical operating frequencies, shank deflections were less in tapered designs than in straight designs. Also, the deflections decreased as the length of the toolholder decreased. However, increasing the body diameter of the toolholder had no significant effect. Accordingly, a number of simple design modifications (changing the diameter and length of the toolholders) are suggested to minimise the fretting condition.     

直接驱动数控铣床双摆头研究

提出了力矩电动机直接驱动五轴联动数控铣床双摆头这一新型驱动技术的研究内容和研究思路.首先,研究力矩电机直接驱动双摆头系统的组成,进行机械结构设计;其次,研究该系统动态参数识别与系统建模;再其次,研究该系统的稳定性分析与参数优化;最后,研究该系统的动态性能与刚度.通过这些研究,能使双摆头取得高速响应、高精度、高动刚度、速度快、加减速过程短、噪声低、效率高的良好指标.     

提高模具型面数控粗加工效率的加工策略

从主轴刀柄选用、刀具选型、切削参数组合、刀具轨迹编程策略等方面进行了分析,围绕提高模具型面铣削粗加工效率的途径进行了实例介绍,对于提高模具数控加工效率具有现实意义。     

Bearing load analysis and control of a motorized high speed spindle

Angular contact ball bearings are the most popular bearing type used in the high speed spindle for machining centers. Because the bearing load is increased rapidly with the raised spindle speed due to the centrifugal force and temperature raise, proper initial preload and especially operating-induced load control of the angular ball bearing is important to the rigidity, accuracy and life of the spindle. The bearing layout, preload mechanism an on-line load bearing control are discussed in this paper. The management of the centrifugal force and thermally-induced bearing loads is especially emphasized. An active bearing load monitoring and control mechanism that consists of an integrated strain-gage load cells and piezoelectric actuators has been developed and tested. This active control and monitoring mechanism on-line adjusts the bearing load according the cutting conditions. Experiments were conducted to identify the proper initial bearing preload range. Optimal preload for the lowest bearing temperature raise existed for a specified spindle speed. The optimum preload, however, should be raised when the operational speed is increased.     

Development of a newly structured variable preload control device for a spindle rolling bearing by using an electromagnet

For high speed and high efficiency machining, the spindle of modern machine tools simultaneously requires high speed and high stiffness characteristics, and its range of use rotation is becoming wider. Both heavy cutting at low speed and light cutting at high speed must be carried out successively in series with a single machine tool spindle. As such, many studies are being carried out on variable preload control methods that apply a preload to a spindle rolling bearing, as an alternative to the existing fixed position preload and constant pressure preload methods. This paper introduces a newly structured variable preload control device that can arbitrarily adjust the preload applied to spindles employing a rolling bearing. The device controls the coil current on an electromagnet and thereby uses the magnetic force between the electromagnet and a magnetic substance to arbitrarily control the preload applied to the rolling bearing during operation. A prototype for the variable preload control device of the proposed structure was created and a functionality test was then carried out with a test bench prepared using a load cell. The operating principle of the proposed device was verified and the interrelationships between the coil current on the electromagnet and the preload applied to rolling bearing were analyzed through the functionality test. Lastly, the fabricated variable preload control device was applied to a prototype of a spindle system, and a rigidity test was carried out. The test results confirmed that the variable preload control device operates properly and smoothly.     

高速精密轧辊磨头液体止推轴承油膜性能的数值分析

高速精密轧辊磨头止推轴承的性能是影响轧辊磨床加工稳定性和精度的重要因素。Roynolds方程是滑动轴承油膜压力计算的基础,文中基于有限差分法,对Roynolds方程进行量纲一化处理,并借助MATLAB软件强大的符号运算、数值计算及图形可视化处理功能,进行编程计算,求解了高速精密轧辊磨头止推轴承油膜的完整二维流动Roynolds方程。求解结果表明:液体静压止推轴承具有很高的承载能力和较高的油膜刚性,保证了磨头主轴的旋转精度和运动精度。研究结果对于高速轧辊磨床的整体设计具有一定的参考价值。     

轴承预紧对机床主轴刚度的影响

阐明了用有限元法分析计算机床主轴组件刚度的步骤和方法,并对主轴刚度进行计算,讨论不同预紧条件下,轴承刚度对主轴性能的影响;并探讨轴承预紧后,增大预紧量对主轴刚度的影响。结果表明:支承轴承预紧的增大使主轴弯曲刚度增幅最大为22%,而对固有频率的影响不明显。     

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。