高速切削加工稳定性研究的现状和发展趋势

论述了国内外高速切削加工稳定性研究的发展现状。介绍了国内外学者此方面的研究工作。对高速切削加工稳定性模型与机理、切削颤振的预防控制和在线监视控制。进行了归纳和分析。并从目前的国情出发。讨论了高速切削加工稳定性研究的发展趋势。     

高速切削加工过程振动预测技术

高速切削加工参数选择不合理会导致切削振动,切削过程中振动引起的不稳定切削会产生一系列不良的影响,切削振动的预测将有助于优化高速切削加工过程,提高切削加工表面质量和加工效率.概述了高速切削加工过程中颤振产生的机理与类型,并分析了切削颤振的影响因素;对切削加工过程稳定性预测进行了报道,重点论述了切削稳定性的影响因素;对切削振动辨识与预测方面的研究成果进行了总结.指出了切削加工过程振动预测技术的未来发展趋势.     

切削颤振研究的关键技术与进展综述

切削颤振是金属切削加工过程中的一种非常复杂的机械振动现象,影响零件加工质量并限制生产率提高.颤振产生的原因和发生、发展规律与切削过程本身以及切削机床动态特性都有着内在的本质联系,长久以来被众多研究者关注.本文就切削颤振在颤振机理、建模、稳定性分析、颤振识别预报以及颤振控制领域的国内外研究成果进行了详细介绍,讨论和分析了...     

高速切削钛合金稳定性模型及极限切深预测

针对TC4钛合金高速加工过程中颤振及切削稳定性问题进行了研究。首先根据闭环加工系统的动力学模型,建立了高速切削过程的稳定性模型,并通过解析计算的方法得到了加工过程中稳定切削极限深度与转速之间的关系。然后采用力锤敲击方法获取了刀具的频响函数,为切削稳定性模型的建立奠定了基础,最后采用切削实验验证了模型的准确性。结果表明:采用高速切削方式加工TC4钛合金能更好的避免加工过程的颤振现象,建立的稳定模型能很好地预测加工过程的稳定性。     

高速加工系统稳定性的研究进展

从切削动力学、颤振稳定性和机床—工具—工件系统的动态特性等方面介绍和分析了高速加工系统稳定性的研究进展与现状。论述了高速加工系统动态特性和切削稳定性研究的重要性和必要性,并提出了今后的主要研究方向。     

铣削加工系统三维稳定性理论研究与进展

切削颤振是高速加工过程中经常遇到的一种现象,而判断稳定切削常用的一种方法就是绘制稳定性图。主要针对国内外铣削加工颤振三维稳定性图和三维稳定性理论研究状况进行了综述,重点给出了Thevenot、U.Bravo和S.Herranz、Tony L.Schmitz和Altintas的稳定性理论。研究指出,为了保证材料的最大去除率,必须研究切削参数对于稳定性的影响,也就是需要研究主轴转速、轴向切深和径向切深对切削颤振影响的三维稳定性图。     

高速加工系统稳定性预测的关键技术研究

从连续切削、断续切削、薄壁件切削及铣刀螺旋角等方面阐述了高速加工系统稳定性的预测方法;对稳定性动态优化及颤振抑制方法进行了分析;并对高速加工系统中出现的各种振动频率进行了讨论.最后指出现在研究的不足和今后研究的主要方向.     

高速切削加工稳定性研究

振动是金属加工过程中的一个复杂问题,其形成的颤振不仅限制了机床加工效率的提高,还对机床和切削刀具造成很大的危害。对数控加工特别是高速加工过程中颤振的研究和控制技术是先进制造技术的重要研究课题,本文介绍了切削动力学建模的两个环节:切削力建模和刀具—工件动力学建模;根据切削力建模方式的不同,将其归纳为基于试验的经验公式建模法、解析建模法和基于人工智能及软件技术切削力建模法;根据铣削加工过程中稳定区域的不同预测方式,切削稳定性分析方法分为时域分析方法、频域分析方法、试验分析方法,并对三种方法的优势和不足进行对比分析;对切削颤振的抑制措施进行了总结介绍;展望了高速切削加工稳定性研究的关键技术,为切削加工振动的理论研究与工业应用提供借鉴和参考。     

高速铣削稳定性的不确定性建模及实验预测

高速铣削加工过程的颤振不稳定性是制约刀具寿命和加工效率的主要因素。传统的颤振稳定性预测模型都假设系统参数是恒定的,但是在实际的高速铣削过程中,影响加工稳定性的参数会随着高主轴转速、高系统动态特性而发生变化。为提高铣削加工精度,以高速铣削加工稳定性为研究对象,考虑参数不确定性的影响,应用棱边定理和排零准则,建立高速铣削变参数稳定性预测数学模型。在此基础上,通过模态测试和辨识铣削力系数获得固有频率及切削系数的变动范围,然后采用数值分析和铣削实验相结合的方式,验证了建立的高速铣削变参数稳定性模型的正确性。     

切削颤振分析与模糊控制实验研究

切削颤振是影响金属切削加工生产率和加工质量的重要因素。建立了金属切削过程的二维颤振数学模型;对颤振的稳定性进行了线性分析和非线性分析;并以颤振位移作为反馈变量,建立了基于二维模糊控制器的颤振控制系统。实验结果表明,该分析与控制对降低加工表面粗糙度具有重要意义。     

高速铣削时颤振的诊断和稳定加工区域的预报

给出一种通过测量加工过程中的噪声来诊断高速铣削时颤振的方法.先测量环境噪声,然后测量加工噪声.理论分析和试验结果表明,如果加工噪声的主谐振频率接近其中一个环境噪声主谐振频率或者是齿频的整数倍,那么系统无颤振,否则有颤振.建立系统结构和铣削过程动力学特征参数的数学模型.根据测出的颤振频率,通过所建模型可解出系统的固有频率、阻尼比和过程参数,并计算出稳定极限曲线.试验证明,该方法能较好地预报高速铣削时的稳定加工区域.     

Prediction of regenerative chatter in the high-speed vertical milling of thin-walled workpiece made of titanium alloy

With the wide application of high-speed cutting technology, high-speed machining approach of titanium alloy has become one of the most effective ways to improve processing efficiency and to reduce the processing cost, but the cutting chatter which often occurs in the cutting process not only affects the machining surface quality but also reduces the production efficiency. Regenerative chatter is a typical phenomenon during actual cutting, and it has the greatest impact on the cutting process. With the purpose of avoiding regenerative chatter and selecting appropriate cutting parameters to achieve a steady cutting process and a high surface quality, it is necessary to determine the critical boundary conditions where chatter occurs. Built on the work of previous theoretical researches of regenerative chatter, this paper utilized Visual C++ software to calculate the chatter stability domain during the finish machining of titanium alloy. It was shown that the border between a stable cut and an unstable cut can be visualized in terms of the axial depth of cut as a function of the spindle speed. Using the result, it can find the specific combination of machining parameters, which lead to the maximum chatter-free material removal rate. In order to verify the result, the high-speed milling experiment of an I-shaped thin-walled workpiece made of titanium alloy was conducted. It revealed that the actual machining result was consistent with the calculation prediction. This study will offer a useful guide for effective parameter selection in future CNC machining applications.     

Chatter stability prediction in milling using time-varying uncertainties

The chatter stability in milling severely affects productivity and quality of machining. Tool wear causes both the cutting coefficient and the process damping coefficient, but also other parameters to change with cutting time. This variation greatly reduces the accuracy of chatter prediction using conventional methods. To solve this problem, we consider the cutting coefficients of the milling system to be both random and time-varying variables and we use the gamma process to predict cutting coefficients for different cutting times. In this paper, a time-varying reliability analysis is introduced to predict chatter stability and chatter reliability in milling. The relationship between stability and reliability is investigated for given depths and spindle speeds in the milling process. We also study the time-varying chatter stability and time-varying chatter reliability methods theoretically and with experiments. The results of this study show that the proposed method can be used to predict chatter with high accuracy for different cutting times.     

考虑极限切削宽度的45钢切削力仿真分析

以高速车削45钢为研究对象,针对高速车削颤振问题,通过绘制稳定性叶瓣图得到无颤切削参数。利用Third Wave AdvantEdge有限元分析软件,基于无颤切削参数设计正交试验,运用极差分析法得到切削用量对各切削力的影响主次顺序和最优组合。根据仿真试验结果,建立了车削力预测模型并检验了回归模型的可靠性。通过单因素试验法分析研究了各切削参数对车削力的影响规律,从减小车削力和提高高速车削加工稳定性方面出发,在所选参数范围内得出了高速车削45钢时的最优参数组合为:v=1200m/min,f=0.05mm/r,ap=0.2mm。     

Chatter stability prediction for high-speed milling through a novel experimental-analytical approach

Chatter prediction is crucial in high-speed milling, since at high speed, a significant increase of productivity can be achieved by selecting optimal set of chatter-free cutting parameters. However, chatter predictive models show reduced accuracy at high speed due to machine dynamics, acquired in stationary condition (i.e., without spindle rotating), but changing with spindle speed. This paper proposes a hybrid experimental-analytical approach to identify tool-tip frequency response functions during cutting operations, with the aim of improving chatter prediction at high speed. The method is composed of an efficient test and an analytical identification technique based on the inversion of chatter predictive model. The proposed technique requires few cutting tests and a microphone to calculate speed-dependent chatter stability in a wide range of spindle speed, without the need of stationary frequency response function (FRF) identification. Numerical and experimental validations are presented to show the method implementation and assess its accuracy. As proven in the paper, computed speed-dependent tool-tip FRF in a specific configuration (i.e., slotting) can be used to predict chatter occurrence in any other conditions with the same tool.     

Hybrid model- and signal-based chatter detection in the milling process

Chatter causes machining instability and reduces productivity in the metal cutting process. It has negative effects on the surface finish, dimensional accuracy, tool life and machine life. Chatter identification is therefore necessary to control, prevent, or eliminate chatter and to determine the stable machining condition. Previous studies of chatter detection used either model-based or signal-based methods, and each of them has its drawback. Model-based methods use cutting dynamics to develop stability lobe diagram to predict the occurrence of chatter, but the off-line stability estimation couldn’t detect chatter in real time. Signal-based methods apply mostly Fourier analysis to the cutting or vibration signals to identify chatter, but they are heuristic methods and do not consider the cutting dynamics. In this study, the model-based and signal-based chatter detection methods were thoroughly investigated. As a result, a hybrid model- and signal-based chatter detection method was proposed. By analyzing the residual between the force measurement and the output of the cutting force model, milling chatter could be detected and identified efficiently during the milling process.

     

切削的稳定界与颤振预报

在文献[1]的基础上,本文导出了无再生颤振、再生颤振及特殊情况下再生颤振的切削稳定界及绝对稳定界公式。指了Tobais公式、Tlusty公式不妥文中指出,k的研究是不完备的。目前许多关于k的说法与事实和实验不符。文中提供了切削与磨擦颤振的统一问题。根据本文给出的公式,作者较成功地预报了切削颤振的发生,因而公式对建立CAM数据库有指导意义。     

切削颤振的动力学模型研究

振动是金属切削加工过程巾经常遇到的一种现象,也是影响零件加工质量和限制生产率提高的主要因素之一。本文在切削颤振机理研究的基础上,对切削颤振的二维稳定性进行了研究,推导出了在稳定性极限条件下,轴向切深和主轴转速的关系,并用Matlab进行了计算仿真。     

Proposal of novel spindle speed variation profile with constant acceleration rate for improvement of chatter stability

Spindle speed variation (SSV) is one of the effective methods which suppresses regenerative chatter. However, regenerative chatter can grow even if SSV is applied. In the previous work, the chatter growth characteristics in SSV were clarified. The chatter frequency changes proportionally to the varying spindle speed, and it causes the change of the magnitude of the dynamic compliance. Hence, chatter can be suppressed through SSV since the dynamic compliance usually reduces as the chatter frequency changes. A greater compliance reduction can be obtained by a higher rate of spindle speeds in two consecutive revolutions at the same angular position, i.e., acceleration rate. From the investigations in the previous work, limitation of the conventionally utilized SSV profiles is found as follows: the acceleration rate always fluctuates with speed variation and the chatter vibration grows where the acceleration rate is insufficient for suppression, and hence suppressing chatter in all sections of SSV is difficult. In this paper, a new SSV profile with a constant acceleration rate, namely CAR-SSV, is proposed to overcome the limitation of chatter stability improvement by utilizing conventional SSV profiles. The magnitude of the acceleration rate is kept constant to realize the chatter suppression effect throughout the cutting process. Through time-domain simulation and cutting experiments, the chatter stability of CAR-SSV is investigated based on the previously introduced chatter stability evaluation indices. Influence of the parameters of CAR-SSV on the stability is investigated, and an appropriate strategy for setting SSV parameters to achieve higher stability is discussed. In addition, in order to verify the effectiveness of the proposed profile, the stabilities of conventional SSV profiles and CAR-SSV are compared through time-domain simulations and cutting experiments.