某型立式加工中心结构动态特性研究

以某型立式加工中心为研究对象,首先进行实物建模并做必要的简化,将其转化为结构力学模型,并进行模态分析,得到了立式加工中心的振型和固有频率等动态特性;分析了主轴箱处在立柱不同位置对立式加工中心固有频率的影响;通过谐响应分析可知,立柱和主轴箱的结构对立式加工中心的模态影响最大;最后进行了试验模态,通过对比有限元和试验模态结果,验证了试验结果的可信性和有限元模型的准确性。在误差允许的范围内,有限元分析结果可以作为加工中心振动特性分析的参考依据,该方法对加工中心的设计优化及相关测试工作具有重要的参考价值。     

HDB-63高速卧式加工中心立柱动静态特性有限元分析

以高速卧式加工中心柱为研究对象,建立了其基于组合体的有限元模型并分析了结构特点.立柱连接着滑架和床身,是加工中心重要的连接部件.为保证加工中心的加工精度和静动态特性,有必要对立柱的静动态特性进行有限元分析,检验立柱的设计是否合理.对立柱进行了静力分析,分析结果表明立柱的变形主要集中在上部.对立柱进行了模态分析,分析结果表明其薄弱环节为两侧支撑.静力分析和模态分析的结果为立柱的结构优化指明了方向.     

基于动态特性分析的KVC800立式加工中心运行优化研究

在数控加工中心设计之初常会考虑固有频率的影响,但由于加工过程中不可避免的误差,对已投入使用的数控加工中心开展动态特性分析,掌握其各阶模态,对于优化加工中心的运行仍必不可少。对KVC800立式加工中心开展了ANSYS有限元模态分析、锤击法试验模态分析以及升速过程中振动信号的瀑布图分析,通过相互对比与验证,发现加工中心存在工作转频内的低阶模态。切削动态测试验证在此低阶模态下工件加工精度略低,为加工中心的优化运行提供了可靠依据。     

某型立式加工中心动态性能测试与优化分析

以某立式加工中心为研究对象,通过模态测试来分析该立式加工中心在动态性能上的薄弱点,并依据测试结论对该立式加工中心进行结构优化,最后对优化后的机床再次进行测试分析。测试结果证明此次优化效果显著,因此基于动态性能测试与优化的流程在立式加工中心的实际设计过程中具有重要的参考价值。     

基于PolyMAX方法的加工中心工作台计算模态与实验模态对比分析

利用ANSYS软件建立加工中心工作台的有限元模型,对工作台模态特性进行分析,得到前3阶模态频率和振型;应用PolyMAX方法对工作台进行实验模态分析.通过对比计算模态与实验模态的分析结果,验证有限元模型的合理性,为工作台结构的合理设计与改进提供理论依据.     

多轴联动龙门式加工中心主体结构有限元分析

采用有限元软件SAMCEF Mecano,建立了多轴联动龙门式加工中心主体结构的仿真模型,基于结合面特性参数数据库,采用用户自定义矩阵来处理机床结合部的接触问题,对加工中心进行了静、动态特性分析,得出了加工中心的静刚度、模态振型、动刚度.找出了机床的薄弱环节.通过建立动态的有限元模型,对加工中心进行了动力学分析,得出不同时刻应力变化云图.验证了静、动态特性分析的正确性.这些内容为进一步的研究加工中心的动态特性、结构优化设计以及轻量化设计提供了重要依据.     

高速立式加工中心动态特性分析及结构改进

利用ANSYS Workbench软件对高速立式加工中心整机进行模态和谐响应分析,获得了感兴趣频段的固有频率.通过对整机各阶模态振型进行分析,找到了整机结构的薄弱环节,并据此对整机结构进行改进,改进后整机的动态性能明显要优于原整机,为进行机床结构的优化设计指出了改进的方向.     

某型号加工中心整机模态的分析测试及预测评价

为了准确、有效、快速地获取某型号加工中心整机的固有频率和振型,结合改进弹簧刚度法与虚拟材料法对某加工中心关键结合面进行了处理,建立了该加工中心的有限元模型。采用有限元分析法获得了该加工中心的前4阶模态参数,以有限元分析结果为指导,确定模态测试的布点密度、测点位置、采样频率、边界条件等试验参数;采用SIMO锤击法对该加工中心进行模态测试,通过比照模态分析与模态测试的结果,修正仿真模型获得更为精确的仿真模型。分析结果表明:使用改进的弹簧刚度法与虚拟材料法比单独使用弹簧刚度法及虚拟材料法能够更加准确地拟合试验结果。最后,根据机床实际工况确定边界条件,以模态仿真结果为依据对机床动态特性进行评价,为后续建立机床适应性评价体系提供了可行、准确的特征参数提取方法。     

基于有限元分析的机床结构优化设计

介绍了对某型号加工中心机床结构的有限元分析。详细分析了整机的前几阶模态。研究后发现由于立柱和支撑板设计的不合理,就会导致机床固有频率较低,振动增大,机床精度下降。针对加工中心机床部件的结构特点,对于立柱,筋板进行结构优选和设计参数优化,并对支撑板采用了拓扑优化和参数优化结合的方法。研究结果表明,通过有限元分析,加工中心机床结构参数得到了较好的优化,从而使整机性能得到了提高。     

DVG850高速立式加工中心主轴箱灵敏度分析

基于Pro/Mechanical,以模态频率为性能指标,对DVG850高速立式加工中心主轴箱进行灵敏度分析,得出各设计变量对主轴箱第一阶固有频率的影响情况,根据主轴箱具体情况对灵敏度分析结果进行评价,为高速立式加工中心主轴箱结构改进或优化设计提供前提依据。     

数控机床切削过程中的动态特性测量方法北大核心

针对高速高精度切削加工过程中机床动态特性分析较为困难的问题,提出一种快速扫频正弦切削法来测量数控机床切削过程中的动态特性。该方法采用车削过程中的切削力作为激振力进行试验模态分析,主要通过以恒定的进给量切削正弦轮廓的圆柱形工件,并线性增加主轴转速,从而将切削力转化为数控机床频率响应函数的激励输入。结果表明:与传统的冲击测试方法对比,快速扫频正弦切削测试的共振峰柔度和频率均有所降低,分别降低了约6.7%和16.7%。此外,通过希尔伯特变换分析,观察到冲击测试和快速扫频正弦切削测试之间有很大的区别。在快速扫频正弦切削测试中,可以直接识别出切削过程中非线性的影响,为准确测量机床切削过程中的动态特性提供了理论依据。     

Estimation of machine-tool dynamic parameters during machining operation through operational modal analysis

The stability of high-speed machining operations determines the reliability of machine tools and the quality of machined parts. Chatter-free cutting conditions are difficult to predict as they require accurately estimated dynamic modal parameters. A spectrogram analysis and impact tests for different configurations of the machine tools were conducted to compare the modal parameters at 0 rpm tests and during machining tests. Variations of between 2% and 8% were observed for the natural frequencies and between 2 and 10 times for the damping ratios.The operational modal analysis (OMA) is considered as a powerful tool for dynamic modal parameter estimations during machining operations. A complete methodology for applying this technique for machining operations was detailed. It was demonstrate how the OMA can be industrially exploited. The proposed approach was successfully applied during the high-speed machining of the 7075-T6 aluminum alloy to extract machine-tool parameters. Two different numerical approaches were used: the autoregressive moving average method (ARMA) and the least square complex exponential method (LSCE), both of which generated similar results. The dynamic parameters found using the operational modal analysis were used to predict machine dynamic stability lobes, and through experimental validation, it was shown that some depths of cut that are stable with standard stability lobes become unstable with dynamic stability lobes.     

基于结合面参数的机床整机有限元建模与分析

基于结合面参数,利用ANSYS建立了AV1200-2五坐标立式铣床整机有限元模型。通过模态试验与有限元计算结果对比分析,验证了文中建模方法的正确性。最后,结合有限元与试验模态分析的结果,初步识别了整机结构的薄弱结合面及薄弱结构,并提出了相应的修改建议。     

Experimental modal analysis using a tracking interferometer

Experimental modal analysis is carried out for machine tools and in various other industries. It is used for dynamic characterization, diagnostics, condition monitoring, design optimization and as comparison data for computation results. 3D-scanning laser Doppler velocimeters and three-axial accelerometers dominate the experimental modal analysis today. This paper presents a method for modal analysis using a tracking interferometer as well for geometric measurement as for simultaneous 3D-vibration measurement with a single laser beam. A holistic measurement procedure is developed, its performance and robustness against external influences is investigated and a benchmark against accelerometers is carried out at a machining center.     

高频响快速刀具伺服系统的免疫重复控制研究

直线电机伺服系统在高档数控加工机床快速刀具伺服应用中,要求系统对于高频响的周期性输入信号具有较好的跟踪能力,又要对于端部效应引起的周期性负载扰动具有一定的抑制能力。针于这一问题,提出了一种基于重复控制和免疫算法相结合的免疫重复控制策略,设计了重复控制器及免疫反馈控制器,对免疫重复控制与只采用重复控制的方法进行了对比分析。结果表明;所采用的控制方案可以在实现高频响的同时能够很好地抑制系统的负载扰动,对高频周期性输入信号具有较好的跟踪性能,且结构简单、计算量适度。     

Identification of weak spots in the metrological investigation of dynamic machine behaviour

Both the measurement of frequency response functions and the modal analysis are established tools for the measurement of the dynamic compliance of machine tools. State of the art measurement technique enables an allocation of dynamic weak points of the machine structure and optimization of the machine design on the basis of these measurement results. In recent applications the metrological investigation is used for the parameterization and the verification of simulation models to describe the dynamic behaviour of machine tools, which demands high standards regarding to the quantitative quality of measurement results. This paper describes the interlaboratory comparison test, which has been carried out at well-known German research institutes and was initiated by the Laboratory for Machine Tools and Production Engineering (WZL) of the RWTH Aachen. In this regard, the question is discussed, to what extent the compliance behaviour of machine structures under real process conditions corresponds to behaviour, determined in metrological investigation under idealized test conditions.     

An approach for measuring the FRF of machine tool structure without knowing any input force

Measuring the dynamics of a machine tool is important for improving its processing or design. In general, the dynamics of the machine tool structure is identified by the experimental modal analysis approaches that require the measurement of both the input loadings and the corresponding structural responses. However, the primary limitation for this method is that the input loadings are difficult or impossible to be measured when the machine tool is under operational conditions. In this paper, a method that is based on random decrement technology was used to identify the operational modal parameters of a machine tool without the knowledge of any of the inputs. To estimate the frequency response functions, FRFs, a structural change method was proposed. The approach is based on the sensitivity of the eigenproperties to structural modifications caused by the drive positions. The proposed method was verified experimentally by traditional hammer tests. Because no elaborate excitation equipment is used, the dynamics of the machine tool structure with arbitrarily feed rate or working position can be easily identified using the proposed active excitation modal analysis method.     

Measurement of structure dynamics using a tracking-interferometer

Measurement of structural dynamics can be used for dynamic characterization, diagnostics, condition monitoring, analyzing sources of vibration problems, design optimization and, finally, as comparison data to improve computation results. Mainly for open surfaces in automotive and aerospace industries the modal testing is often performed using laser vibrometers. In the case of partially closed structures as machine tools, modal analyses comprises the three dimensional vibration measurements at up to several hundred points of the structure and is classically conducted using accelerometers. This paper presents a novel approach to perform modal analyses using a tracking-interferometer. The modal analysis is shortly introduced along with the two mentioned methods. Further, the functionality of tracking-interferometers is discussed as well as the basics for their application in dynamic measurement. One-dimensional measurements using a tracking interferometer are conducted and benchmarked against other devices. Three-dimensional measurements are presented including the necessary coordinate transformation. A small modal analysis is demonstrated. Finally, a measurement strategy for fast modal testing is suggested and additional functionalities required for the tracking interferometer are discussed.     

直接驱动型磁悬浮直线进给单元

介绍一种机床功能部件——直接驱动型磁悬浮直线进给单元的原理与特点,该功能部件由直线电动机提供驱动力,由磁悬浮导轨导向和承载工作台,可满足数控机床高速化、精密化要求。并简述其研究现状和分析其关键技术问题。