机床主轴的动刚性评估法

基于动刚性与固有频率的联系性，在安装在主轴上的实验棒上加振动脉冲后测其固有频率的方法求出主轴的动刚性，提出了一种机床主轴的动刚性的检查法，并对被测的机床又进行切削实验，调查了机床主轴的刚度与加工面粗糙度的关系。     

机床主轴系统动态性能的探讨

一、概述机床主轴前端装有刀具或工件,直接参加切削加工,因而主轴系统是影响机床的加工质量和生产率的一个关健部件。主轴系统的变形占机床系统总变形的50％左右,机床系统的动柔度主要决定于主轴系统的动态性能。影响机床动态性能的因素有以下诸项:     

数控机床主轴最佳跨距求解与有限元分析

主轴部件是机床最重要部件之一,主轴跨距是影响机床动、静刚度的重要因素。对拟开发的某型数控车床主轴进行研究,通过对二支承非卸荷式皮带轮传动主轴进行静力分析的基础上,建立了数学模型,利用卡丹公式对主轴最佳跨距和静刚度进行求解;通过ANSYS Workbench软件对主轴部件进行了有限元分析,证明主轴最佳跨距的可行性。     

微小型机床主轴部件的特性分析

主轴作为机床的关键性部件其动静态特性对加工质量起着不可忽视的作用因此,本文针对机床的主轴部件进行了空气动力学分析,得到空气主轴的承载力和刚度,并将刀具考虑进来,研究了主轴的静力学特性和动态特性。     

国外高速机床用电主轴概况

高速机床的应用领域正日趋扩大 ,许多切削工序 (如车、磨、钻、铣、镗、扩孔和铰孔等 )相继使用高速机床 ;另一方面 ,几乎任何材料 ,如钢、铸铁、轻金属、有色金属、难加工金属、合金及塑料等都可用高速切削加工方法加工。在高速机床的部件中 ,主轴结构对制品的加工质量和机床加工效率有重要影响。高速机床的主轴结构越来越多地使用电主轴。1　电主轴的支承在生产高速电主轴部件时 ,对其静态、动态稳定性有严格要求。在滚动轴承、静液压轴承、动液压轴承和磁性轴承的基础上 ,可设计以下几种主轴支承。1 .1　径向支承滚动轴承在使用滚动轴承…     

一种基于稳定性图的车铣复合机床切削稳定性研究及优化

为提高车铣复合机床的切削稳定性,避免切削过程中的颤振问题,文中以稳定性叶瓣图（以下简称稳定性图）为基础,研究了切削微型零件过程中的颤振问题。通过对车铣复合机床机构和机床模型的分析,得到了机床动态振动模型和机床颤振的数学模型。同时通过锤击试验方法,得到了刀具与工件系统的传递函数,构建了车铣复合机床的稳定性图。最后对机床主轴部件、机床后轴部件和高频铣削部件的稳定区间进行了研究,该实验研究结果指导和优化了车铣加工切削微型零件的参数选择。     

用模态分析方法研究主轴部件质量分布对动特性的影响

本文讨论了研究主轴部件质量分布对其动特性影响规律的模态分析方法。发现质量分布对不同阶次的固有频率和模态柔度的影响存在着较大差异。指出正确调整主轴部件的质量分布,将有助于均化模态柔度在静柔度中所占比重,从而提高机床的切削稳定性。引用实验结果,初步证实了本文的结论。     

机床优化设计(七)

主轴部件优化设计(一) 评价主轴部件主要性能的指标有以下几个。 1.主轴部件动特性。描述其动特性的参数有:切削点受迫振动的振幅幅值｛X｝,要求在允许值内;切削点的动柔度W0,0,其负实部越小,抵抗自激振动的能力越强;主轴部件固有频率,要避开频率禁区。 2.满足系统静刚度要求。 3.在满足上述动、静特性要求下,主轴部件重量最轻。 为优化主轴部件,必须首先计算主轴部件的参数,即计算系统固有频率和主振型;计算切削点的动柔度和交叉动柔度等。 计算主轴部件常用的数学模型有:集中参数模型;分布质量梁模型;有限元模型。分述如下。 一、靠中参…     

切削机床的驱动也要适应于超高速切削技术

现代机床的可控主驱动,由于其高效组成部件(如电动机、主轴、离合器和轴承)的优良使用性能和经济效果的迅速转化,目前在技术发展上已达到了一个很高的水平。 切削机床的主驱动产生切削运动,提供实现工艺所要求的切削功率和切削力矩。占绝大部分的机床产生回转的切削运动,例如车床、钻床和铣床。典型的结构方案由结构部件驱动电动机(能量馈给和转换)、机械传递部件和转换部件(能量传递)和主轴(能量转换)组成(图1)。 至今一个较高程度柔性的要求以及保证机床要有较高的生产效率     

机械加工工艺系统动刚度加工精度误差递减规律

所谓动刚度是指机床在加工状况下，系统受力与变形之比，或者说机床在加工状态下所具有的刚度。实验证明，机床在高速动转下，有关部件的刚度将有所增加。例如，普通车床主轴箱部件的刚度，当转速增至到1200r/min时，其动态刚度比静态刚度增加20％～25％，低速n<500r/min时，刚度增加不明显。据分析，高速状态下主轴部件刚度增加的原因有： (1)高速下主轴产生了陀螺效应，起了阻止主轴位移作用； (2)高速下轴承内润滑油膜对主轴径向位移产生了抗力。     

机床的主轴单元（下）

通过回顾机床主轴发展历程,指出电主轴在高端数控机床的应用日益广泛。继而详尽地阐述了机床主轴单元的设计要点,包括轴承、润滑和冷却以及刀具接口等。接着对主轴的静动态和热性能分析以及建模仿真进行了全面介绍。最后指出主轴的工况监控、智能化和自适应控制是新一代电主轴的重要特征和未来发展趋势。     

Simulation of dynamic properties of a spindle and tool system coupled with a machine tool frame

The cutting performance relates to the dynamic properties of the whole system of the tool, spindle, and machine tool frame. The impact of the machine frame properties on the dynamic properties at the tool end point is studied both experimentally and using a coupled simulation model. Coupled model of the whole mechanical system is created as a system joining the spindle detailed model and machine frame FE model. Shift in the spindle and tool system dynamic properties, related to the machine frame properties, is proved using the coupled model. Experimental verification of the FRF evaluated at the tool is extended also by cutting tests. Good match of the simulated dynamic properties of the whole system with the real behavior is found.     

车削Inconel 625锯齿形切屑形成对颤振影响的试验研究

为研究高温合金Inconel 625车削过程中锯齿形切屑的产生对颤振的影响,本文通过有限元软件对车削刀具、机床主轴等部件进行模态仿真,获取对应的模态频率;进行不同切削参数的车削试验,采集加速度信号并进行频域分析以获取其FFT功率谱。通过超景深显微镜观察切屑形态,并计算不同切削参数下的切屑锯齿化频率。对比仿真和试验结果发现:当切屑锯齿化频率接近于车床某部件的主振频率时,产生了较大的颤振峰值,这说明锯齿形切屑的产生会诱导切削颤振发生,对切削过程稳定性产生了不利的影响。     

DYNAMICS ANALYSIS OF SPECIAL STRUCTURE OF MILLING-HEAD MACHINE TOOL

The milling-head machine tool is a sophisticated and high-quality machine tool of which the spindle system is made up of special multi-element structure. Two special mechanical configurations make the cutting performance of the machine tool decline. One is the milling head spindle supported on two sets of complex bearings. The mechanical dynamic rigidity of milling head structure is researched on designed digital prototype with finite element analysis（FEA） and modal synthesis analysis （ MSA ） for identifying the weak structures. The other is the ram structure hanging on milling head. The structure is researched to get dynamic performance on cutting at different ram extending positions. The analysis results on spindle and ram are used to improve the mechanical configurations and structure in design. The machine tool is built up with modified structure and gets better dynamic rigidity than it was before.     

Analysis of the machining stability of a milling machine considering the effect of machine frame structure and spindle bearings: experimental and finite element approaches

Chatter vibration has been a troublesome problem for a machine tool toward the high precision and high-speed machining. Essentially, the machining performance is determined by the dynamic characteristics of the machine tool structure and dynamics of cutting process of spindle tool. Prediction of the dynamic behavior at spindle tool tip is therefore of importance for assessing the machining stability of a machine tool at design stage. This study was aimed to evaluate the machining stability of a vertical milling system under the interactive influence of the spindle unit and the machine frame structure. To this end, a realistic finite element model of a vertical milling tool was generated by incorporating the spindle-bearing model into the head stock mounted on machine frame. The influences of the dynamics of spindle-bearing system and the machine frame structure were investigated respectively. Current results show that the machine tool spindle system demonstrates different dynamic behaviors at different frequency ranges, which are also characterized as structural modes and spindle modes, respectively. In particular, the maximum compliance of spindle tool tip was found to occur at the bending vibrations of spindle shaft and vary with the preload amount of spindle bearing. The machining stabilities were predicted to different extent, depending on the exciting modes which could be related to the influences of machine frame and spindle unit.     

Comprehensive measurement and evaluation system of high-speed motorized spindle

Reducing the manufacturing time is the trend of high-precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. The high-speed motorized spindle is the most critical part and becoming more widely used in the machine tool at present, and its precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and effects of the spindle’s thermal deformations; hence, how to roundly measure and objectively evaluate high-speed spindle is an imminence question of it because the comprehensive dynamic properties and evaluation system of spindles directly affect the cutting ability of the whole machine tool before they are manufactured. This paper presents a comprehensive measurement and evaluation system of high-speed motorized spindle, which reflects the overall performance of motorized spindle and bases on international standard.     

基于模态柔度和能量分布的机床动态优化设计

使机床切削点动柔度最大值在整个工作频率范围内最小,是机床实现无颤振稳定切削和高精度切削加工的要求,也是对其进行动态优化设计所应达到的目标。基于模态柔度和能量分布的机床结构动态优化设计原理,实现了一种以降低切削点交叉动柔度值为目标的优化方法。该方法利用切削点交叉动柔度与模态柔度的关系,首先寻找薄弱模态,再分析薄弱模态上各部件和环节的能量分布,确定该模态上的薄弱环节,然后在一定的约束条件下,改进这些环节的设计参数,从而实现优化目标。以某型万能工具铣床为例,在整机建模分析计算的基础上,阐述了该优化方法的具体应用。通过模态柔度和能量分布计算,判明该机床的薄弱环节是横梁-水平主轴体系统,针对薄弱环节设计参数的改进实现其质量和刚度的优化,优化后的静柔度和模态柔度都有较大的降低,而固有频率则相应提高,切削点动柔度的最大值降低近18%。并在此基础上进行结构改进设计,改进前后机床的谐响应分析和切削试验对比结果表明优化方法有效地改善了机床的动态性能,再生颤振稳定性得到大幅提高。     

Modelling and experimental investigation of spindle and cutter dynamics for a high-precision machining center

The geometric quality of high-precision parts is highly dependent on the dynamic performance of the entire machining system, which is determined by the interrelated dynamics of machine tool mechanical structure and cutting process. This performance is of great importance in advanced, high-precision manufacturing processes, including aerospace and biomedical applications. In this paper, the dynamics of the combined spindle/cutter system, a major component of any machine tool, is identified using impact testing techniques and is successfully approximated by a second-order linear model. Results of computer simulations of machining processes that include the identified spindle/cutter dynamics show a significant influence on the quality of the final product. From this, it is concluded that, for precision workpieces, the dynamics of the spindle and cutter system will have to be taken into account in order to improve future machining controls and processes.     

Experiences with the master axis method for measuring spindle error motions

In this paper, the master axis method of machine tool spindle measurement is described. This method allows spindle measurements to be carried out at speed and under load. For example, a radial load representing the cutting force in a turning operation can be conveniently applied during characterization of a lathe spindle. The synchronous and asynchronous error motions have been observed to vary in both magnitude and shape with changes in load. Test results from both static and dynamic loads during testing are shown to demonstrate the utility of the method.     

HSK-100A型刀柄／主轴联接性能分析

将机床主轴与刀具相联接的刀柄是影响机床加工精度、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,建立了HSK-100A型刀柄的三维实体模型,同时利用有限元方法,对影响HSK-100A型刀柄／主轴联接性能的参数进行了分析,为HSK刀柄的实际应用提供一定的依据及指导。