模具平面铣削加工动态仿真研究

在平面铣削颤振产生机理的基础上,简单论述了一种更精确有效的动态铣削力理论模型的建立过程,该模型充分考虑瞬态切屑的厚度及有效前角对动态铣削力的影响。在此基础上,运用数字仿真技术在频域内建立起动态铣削力和刀具-工件系统的相对振动位移的计算机仿真模型。利用该仿真模型,可以实时显示不同工艺参数和加工参数状态下动态铣削力的数值及其功率谱密度图形以及刀具-工件系统的动态振动位移图形。仿真结果将为预测和消除铣削过程的颤振现象,保证加工质量和加工效率,延长刀具使用寿命提供可靠的依据。     

基于加工参数优化的低刚度工件铣削稳定性分析

铣削振动是低刚度工件在铣削过程中广泛存在的问题,以槽式光热发电用扭矩管为模型,通过对加工过程中的颤振原理进行分析,针对低刚度工件的铣削加工特点,在考虑铣刀和工件动态耦合特性的基础上,建立低刚度工件铣削稳定性理论模型,并绘制频域铣削稳定性图。基于叶瓣图,提出一种通过优选切削参数来控制颤振的方法,获取了避免加工颤振的理论加工参数,通过MATLAB/Simulink模块建立低刚度工件铣削加工系统的模拟仿真试验,以验证叶瓣图对于铣削参数优化的指导性。本研究可为低刚度工件铣削加工参数优化和抑制铣削颤振提供参考,对提高低刚度工件铣削加工效率和质量有重要意义。     

时滞效应对铣削系统稳定性的影响

分析时滞效应对铣削系统稳定性的影响,揭示铣削再生型颤振发生的根本原因。铣削再生型颤振来源于系统内部的时滞反馈,应用劳思判据,分析铣削系统发生颤振前后系统刚度和阻尼的变化,得出极限切深。实验结果表明,笔者提出的分析方法简明可行,并能清晰地阐述颤振发生的物理本质。最后通过分析相关案例,体现了该方法的工程应用价值。     

考虑刀具和工件动态耦合特性的薄壁件铣削稳定性研究

针对薄壁零件加工过程中的颤振现象,考虑刀具和工件的动态耦合特性,建立多自由度铣削颤振模型,并针对刀具和壁板类薄壁工件进行模态实验,获取相对传递函数,采用解析法(ZO A)绘制了颤振稳定性叶瓣图。通过对比仅考虑刀具或工件的动态特性,最终得到薄壁件多自由度系统稳定性极限预测模型。该模型精确绘制了薄壁件铣削稳定性叶瓣图,对以后的生产加工提供指导。     

切削用量对铣削非标内螺纹刀具磨损的影响

与传统螺纹加工方法相比,铣削螺纹不仅具有较高的加工精度和加工效率,而且不受螺纹结构的制约,可较为自由地选取合理的加工参数。应用DEFORM-3D软件对铣削非标内螺纹刀具磨损进行仿真,运用正交仿真试验研究切削速度、最大切削厚度和径向切削深度等切削用量对刀具磨损的影响,并对加工参数进行了优化。结果表明:切削刃圆角处刀具磨损最严重,在研究范围内,径向切削深度对刀具磨损的影响最大。     

圆周铣削加工动态和静态铣削力MATLAB仿真分析研究

基于圆周立铣刀在铣削加工中静态和动态切削力分布对工件尺寸精度有较大影响的现状,对静态和动态铣削力模型进行建模研究,建立有效铣削力分布预测仿真,并对静态和动态铣削力仿真结果进行对比分析,研究结果表明在铣削过程中动态铣削力分布对工件已加工部分的尺寸精度预测较静态铣削力预测有较大优势,通过改变刀具齿数、进给速度、径向切深3个...     

数控型腔铣削加工稳定性预测

数控型腔铣削加工过程中,铣刀进入拐角时,刀具-工件间啮合信息的变化通常会引起颤振。针对这一状况,在用半离散算法对刀具-工件啮合状况恒定铣削加工稳定性预测的基础上,结合数控型腔铣削加工过程中加工路径引起的刀具-工件间啮合信息的变化,针对给定的加工路径提出了型腔铣削加工稳定性预测的方法。试验证明,该方法能在数控加工时对型腔加工过程中的铣削稳定性进行成功预测。     

面向机器人铣削加工的刀尖动态特性分析与稳定性预测

在大型复杂构件机器人铣削加工过程中,由于机器人结构刚度较低、末端负载配置复杂以及工件局部弱刚性等问题,导致机器人铣削加工过程中极易发生颤振现象,进而影响工件的表面加工质量。而机器人铣削加工的稳定性主要取决于其刀尖动态特性,因此提出了一种面向机器人铣削加工的刀尖频响函数(FRF)预测方法,能够实现任意姿态下的刀尖频响预测,进而实现机器人铣削加工稳定性预测,在通过加工参数优化来进一步提升工件表面加工质量。首先,提出了一种基于非线性最小二乘法的加权叠加法,减少了实验量并放宽了对实验位姿的要求。然后,给定任意多个基准实验姿态实测的刀尖频响函数,所提出的模型就能够预测出一定工作空间范围内任意目标姿态下的机器人刀尖频响函数。接着又提出了一种线性化模态参数叠加法,避免了频响函数直接叠加产生的多模态现象,提高了预测准确率。最后,通过开展机器人模态实验与铣削加工试验,验证了该模型的准确性和实用性,进而通过加工参数进一步优化实现了加工质量提升。     

大悬伸工况下刀具铣削稳定性的影响研究

针对大悬伸工况下铣刀加工稳定性差的问题,对铣削过程中的刀具刚性进行仿真分析。结合大悬伸工况下的实际加工情况,对刀具进行简化并建模,建立用于大悬伸加工的铣刀模型。选择铣刀片前角、加工主轴转速和加工进给速率三个主要因素进行有限元仿真实验。基于DEFORM软件分析加工过程中的平均扭矩和径向载荷等,以提升刀具刚性为优化目标,得到最适合的加工参数。分析单个刀片铣削过程的受力变化趋势,确定加工过程中最大载荷出现的大致位置。     

翻板卧式加工中心铣削颤振稳定性的影响因素研究

以某翻板卧式加工中心为研究对象,基于铣削颤振稳定性叶瓣图理论,通过实验与仿真结合的方法得到机床铣削稳定性的影响因素及变化规律,为工程人员提供参考.首先通过敲击实验获取刀尖点频响函数,再通过ANSYS Workbench中使用虚拟材料轴承的谐响应仿真获取频响函数,对比实验与仿真的结果,得到刀尖频晌函数的影响因素.再由刀尖...     

基于MATLAB的铣削加工颤振稳定域仿真算法及实现

针对国内数控铣削加工工艺参数选择存在的问题,基于动态铣削力建模和颤振稳定域分析计算,以MATLAB为开发工具,实现了铣削加工颤振稳定域仿真算法.通过模态锤击实验获得的频响函数,仿真出了整个加工系统的颤振稳定域图形,为进行铣削加工切削参数选择和优化提供了理论依据.验证实验证实了仿真算法的有效性和准确性,仿真方法在工厂得到了实际应用并取得了良好的应用效果.     

Active suppression of chatter in peripheral milling. Part II. Application of fuzzy control

In this paper, a feasibility study is conducted where fuzzy logic control is investigated to actively vary spindle speed modulation parameters for chatter suppression. A justification for using fuzzy control is given, as well as a brief synopsis of the fuzzy inferencing mechanism. Proportional and proportional-integral fuzzy control algorithms are developed. The set point in these controllers is established from experimental observations and measurements of the machined surfaces. Controller performance is tested by simulating changes in the axial depth of cut from a stable depth to 20% and 50% beyond the stable limit for constant speed cutting. It was found that both controllers were able to regulate the vibration in the milling process, however, the proportional-integral controller generally exhibited more desirable performance characteristics.     

Active suppression of chatter in peripheral milling Part 1. A statistical indicator to evaluate the spindle speed modulation method

This work investigates the potential of employing the spindle speed modulation method for real-time control of chatter in peripheral milling. The first part of the study concentrates on developing a measurable chatter indicator which can quantify the relative vibration suppression properties of various speed modulation parameters. Experimental and simulation runs have shown that this indicator provides a well-behaved estimate of the relative cutting condition. The simulation and the experimental set-up for implementing spindle speed modulation are described. Different amplitude-frequency combinations of sinusoidal fluctuations were tested at 20% and 50% beyond the limit of stability both numerically and experimentally with steel workpieces. They showed higher vibration suppression with increased values of speed modulation parameters, which is a general trend that was also reported in other works conducted under different environments.     

实用三弧段等距型面轴的数控铣削仿真研究

从分析实用等距曲线的构成入手,推导出实用三弧段等距型面的大圆弧半径计算公式和型面曲线的数学模型,应用M asterCAM软件进行二维图形的建模,并进行数控铣削仿真,最后生成NC数控加工程序。     

精密数控机床铣刀故障监测方法的研究

刀具在加工过程中不可避免的存在着磨损和破损现象,刀具的消耗直接导致工件精度下降和生产成本增加。开展了一系列实验,深入研究刀具状态监测方法,构建了新型铣削过程刀具磨损监测试验系统。通过振动传感器和声发射传感器对铣削过程中不同磨损程度刀具的信号进行检测、采集、分析。选择对刀具磨损状态反映敏感的特征量。采用BP神经网络,建立刀具磨损特征向量与刀具磨损状态之间的非线性映射关系。     

Modeling dynamics and stability of variable pitch and helix milling tools for development of a design method to maximize chatter stability

Chatter is one of the major limitations in milling operations causing poor quality and reduced productivity. Stability diagrams can be used to identify deep stable pockets which usually occur at high spindle speeds. However, the required high cutting speeds may not be applied in some cases due to machinability or machine tool limitations. It is known that variable pitch and helix tools help suppressing chatter even at low cutting speeds. These tools may offer high productivity if they are properly designed. The literature on variable geometry milling tools is mainly limited to modelling and simulation whereas for industrial applications design guidelines are needed for selection of variation pattern and amount which is the focus of this paper. Dynamics and stability of variable pitch and helix tools are modelled and solved in frequency domain as well as using Semi-Discretization Method employing multiple delays. A practical but accurate design method is presented for selection of the best variation combination to maximize chatter free material removal rate without using time consuming computer simulations. Increased stability with the tools designed using the proposed method is demonstrated by several examples which are verified experimentally.     

薄壁零件的高速铣削稳定性研究

薄壁结构零件在加工过程中极易发生变形和切削振动,这对提高加工质量和加工效率十分不利.在考虑刀具和工件两个方向自由度的基础上,分析了薄壁零件的动态铣削模型.针对2A12铝合金薄壁结构零件,利用MIKRON UCPDUR0800 高速加工中心和相关仪器、软件,通过铣削力辨识实验和模态实验,进行了高速铣削薄壁零件的稳定域分析和实验验证.     

Monitoring of tool fracture in milling

For untended manufacturing operations, in-process monitoring of tool fracture plays a critically important role. A tool fracture feature in the spectrum of the displacement signal of the spindle in milling has been discovered. Therefore, a new signal processing algorithm called the band-limited average energy method using the tool fracture feature to monitor tool fracture is proposed. The energy content of the tool fracture feature is extracted and normalised to detect tool fracture. It is shown, by theoretical studies and experimental results, that tool fracture can be detected under varying cutting conditions in milling.     

Analysis of force patterns and tool life in milling operations

The paper describes the practical effects of the operating parameters in the milling operation. Experiments have been conducted to measure cutting force and tool life under dry conditions. Based on the experimental results, three mathematical models have been developed: Force, TLife and Force/TLife. Further analyses have been conducted on the cutting force patterns: seasonal pattern and nonlinear trend. A process optimisation that is based on the minimum production cost has been applied to relate Force model, TLife model and machinability criteria, such as power consumption, cutting parameters and surface roughness.Nomenclature C _w cost of workpiece ($) - C _s set-up cost ($) - C _m machining cost ($) - C _o overhead cost ($) - C _r tool replacement cost ($) - C _t tool cost ($) - D diameter of the cutter (inch) - d depth of cut per pass (inch) - d ₀ required depth (inch) - e _t random error attth sample - F cutting force (N) - f feedrate (ipm) - L length of workpiece (inch) - N spindle speed (r.p.m.) - n number of teeth - P power of the motor (h.p.) - R surface roughness (µm) - R _e real part of a complex function - T tool life (min) - t sample number - t _m machining time (s) - t ₀ overhead time (s) - t _r tool replacement time (s) - t _s set-up time (s) - U _i unit cost of itemi ($/unit)v - v cutting speed (i.p.m.)     

微铣削刀具磨损研究现状

在微制造领域,微铣削因具有加工材料的多样性和能实现三维曲面加工的独特优势而受到越来越多学者的关注,但是微铣刀的快速磨损严重影响了微铣削技术的应用.研究表明微铣刀的磨损主要发生在刀尖部位,刀具磨损呈现显著的尺度效应.分析了微铣刀的磨损机理、刀具磨损的影响因素和改善措施以及刀具磨损状态的监控,并指出了今后研究值得注意的发展方向.