Influence of Cutting and Geometrical Parameters on the Cutting Force in Milling

This paper presents a numerical modelling of the dynamic behaviour of the Machine-Tool-Part system (MOP) in milling. The numerical study of such complex structure requires the use of sophisticated method like finite elements one. Simulation is employed to predict cutting forces and dynamic response of Machine-Tool-Part system (MOP) during end-milling operation. Finally, spectral analysis is presented to see the influence of feed direction in the vibration.

Experimental Study on Titanium Alloy Cutting Property and Wear Mechanism with Circular-arc Milling Cutters

Titanium alloy has been applied in the field of aerospace manufacturing for its high specific strength and hardness.Nonetheless,these properties also cause general problems in the machining,such as processing inefficiency,serious wear,poor workpiece face quality,etc.Aiming at the above problems,this paper carried out a comparative experimental study on titanium alloy milling based on the CAMCand BEMC.The variation law of cutting force and wear morphology of the two tools were obtained,and the wear mechanism and the effect of wear on machining quality were analyzed.The conclusion is that in contrast with BEMC,under the action of cutting thickness thinning mechanism,the force of CAMC was less,and its fluctuation was more stable.The flank wear was uniform and near the cutting edge,and the wear rate was slower.In the early period,the wear mechanism of CAMC was mainly adhesion.Gradually,oxidative wear also occurred with milling.Furthermore,the surface residual height of CAMC was lower.There is no obvious peak and trough accompanied by fewer surface defects.

Development of micro milling force model and cutting parameter optimization

Taking the minimum chip thickness effect,cutter deflection,and spindle run-out into account,a micro milling force model and a method to determine the optimal micro milling parameters were developed.The micro milling force model was derived as a function of the cutting coefficients and the instantaneous projected cutting area that was determined based on the machining parameters and the rotation trajectory of the cutter edges.When an allowable micro cutter deflection is defined,the maximum allowable cutting force can be determined.The optimal machining parameters can then be computed based on the cutting force model for better machining efficiency and accuracy.To verify the proposed cutting force model and the method to determine the optimal cutting parameters,micro-milling experiments were conducted,and the results show the feasibility and effectiveness of the model and method.

Analytical model of cutting force in axial ultrasonic vibration-assisted milling in-situ TiB_(2)/7050Al PRMMCs

Ultrasonic vibration-assisted milling has been widely applied in machining the difficultto-cut materials owing to the remarkable improvements in reducing the cutting force.However,analytical models to reveal the mechanism and predict the cutting force of ultrasonic vibrationassisted milling metal matrix composites are still needed to be developed.In this paper,an analytical model of cutting force was established for ultrasonic vibration-assisted milling in-situ TiB_(2)/7050 Al metal matrix composites.During modeling,change of motion of the cutting tool,contact of toolchip-workpiece and acceleration of the chip caused by ultrasonic vibration was considered based on equivalent oblique cutting model.Meanwhile,material properties,tool geometry,cutting parameters and vibration parameters were taken into consideration.Furthermore,the developed analytical force model was validated with and without ultrasonic vibration milling experiments on in-situ TiB_(2)/7050 Al metal matrix composites.The predicted cutting forces show to be consistent well with the measured cutting forces.Besides,the relative error of instantaneous maximum forces between the predicted and measured data is from 0.4%to 15.1%.The analytical model is significant for cutting force prediction not only in ultrasonic-vibration assisted milling but also in conventional milling in-situ TiB_(2)/7050 Al metal matrix composites,which was proved with general applicability.

3D finite element prediction of chip flow, burr formation, and cutting forces in micro end-milling of aluminum 6061-T6

Abstract Predictive models for machining operations have been significantly improved through numerous methods in recent decades. This study proposed a 3D finite element modeling （3D FEM） approach for the micro end-milling orAl6061-T6. Finite element （FE） simulations were performed under different cutting conditions to obtain realistic numerical predictions of chip flow, burr formation, and cutting forces. FE modeling displayed notable advantages, such as capability to easily handle any type of tool geometry and any side effect on chip formation, including thermal aspect and material property changes. The proposed 3D FE model considers the effects ofmiU helix angle and cutting edge radius on the chip. The prediction capability of the FE model was validated by comparing numerical model and experimental test results. Burr dimension trends were correlated with force profile shapes. However, the FE predictions overestimated the real force magnitude. This overestimation indicates that the model requires further development.

Mechanistic identification of cutting force coefficients in bull-nose milling process

An improved method to determine cutting force coefficients for bull-nose cutters is proposed based on the semi-mechanistic cutting force model. Due to variations of cutting speed along the tool axis in bull-nose milling, they affect coefficients significantly and may bring remarkable discrepancies in the prediction of cutting forces. Firstly, the bull-nose cutter is regarded as a finite number of axial discs piled up along the tool axis, and the rigid cutting force model is exerted. Then through discretization along cutting edges, the cutting force related to each element is recalculated, which equals to differential force value between the current and previous elements. In addition, coefficient identification adopts the cubic polynomial fitting method with the slice elevation as its horizontal axis. By calculating relations of cutting speed and cutting depth, the influences of speed variations on cutting force can be derived. Thereby, several tests are conducted to calibrate the coefficients using the improved method, which are applied to later force predictions. Eventually, experimental evaluations are discussed to verify the effectiveness. Compared to the conventional method, the results are more accurate and show satisfactory consistency with the simulations. For further applications, the method is instructive to predict the cutting forces in bull-nose milling with lead or tilt angles and can be extended to the selection of cutting parameters.

The Extraction Method of Cutting Engagement in Ball-end Milling Simulation

Ball-end mill is widely used in workpiece processi ng with free-form surfaces. Such models that can predict processing character istics precisely are very necessary to the aim of cost reducing, quality improvi ng and productivity progressing, the cutting force prediction is the most import ant among these models. To explore the physical essence of metal cutting, model researchers commonly simplify the geometric conditions in cutting process, and a ssume that the geometric parameters that are needed to solve the physical models have already been predefined, so it results in the separation between model res earch and practical application. In this paper, for the representative cutting f orce models of ball end milling, a new extraction method of geometric parameters is suggested, which makes it possible for physical model to actually serve for the practical manufacturing, and take in the inspection of real production.

New Mathematical Method for the Determination of Cutter Runout Parameters in Flat-end Milling

The cutting force prediction is essential to optimize the process parameters of machining such as feed rate optimization, etc. Due to the significant influences of the runout effect on cutting force variation in milling process, it is necessary to incorporate the cutter runout parameters into the prediction model of cutting forces. However, the determination of cutter runout parameters is still a challenge task until now. In this paper, cutting process geometry models, such as uncut chip thickness and pitch angle, are established based on the true trajectory of the cutting edge considering the cutter runout effect. A new algorithm is then presented to compute the cutter runout parameters for flat-end mill utilizing the sampled data of cutting forces and derived process geometry parameters. Further, three-axis and five-axis milling experiments were conducted on a machining centre, and resulting cutting forces were sampled by a three-component dynamometer. After computing the corresponding cutter runout parameters, cutter forces are simulated embracing the cutter runout parameters obtained from the proposed algorithm. The predicted cutting forces show good agreements with the sampled data both in magnitude and shape, which validates the feasibility and effectivity of the proposed new algorithm of determining cutter runout parameters and the new way to accurately predict cutting forces. The proposed method for computing the cutter runout parameters provides the significant references for the cutting force prediction in the cutting process.

Cutting edge curve models for equal pitch cutters and their applications

A mathematic model is established using infinitesimal geometry for the cutting edge design of special milling cutters which use equal lead helix as cutting edges; equations are given for front-end and proclitic surface of revolution of ball pillar milling cutters, ball taper milling cutters and angularly conical milling cutters; and corresponding models are established for the continuity cutting edge curves of milling cutters. Typical examples are given to illustrate the applications of mathematic models, which prove the correctness and applicability of these geometric models.

基于热-力耦合理论的刀具结构设计

本文提出一种基于热—力耦合理论的刀具结构设计方法,基于DEFROM 2D/3D软件设计通过硬质合金平头倒角立铣刀,并进行高速铣削7075合金钢的仿真实验,在主轴转速为4000r/min、进给速度为2000mm/min、切削深度为0.1mm的参数下,对影响切削力和切削热的主要刀具结构参数(前角、后角、螺旋角及刀具刃数)进行了仿真研究。研究表明,在此工艺环境下,当结构参数为前角15°、后角10°、螺旋角35°及四刃的刀具齿数时,设计刀具相较于普通刀具的最大切削力下降4.1%,平均切削力下降5%,切削热下降7.4%。

基于刀齿轨迹模型的五轴侧铣加工铣削力预测

在五轴侧铣加工过程中刀具的刀轴姿态变化复杂,导致瞬时切屑厚度计算困难。为提高切削力的预测精度,首先通过五轴侧铣几何模型描述了圆柱铣刀的刀齿运动轨迹,在建立微元切削力模型后,提出了一种瞬时切屑厚度的计算方法,计算当前切削刃上切削点到前几个刀齿回转圆柱面的映射距离,并在齐次坐标变换下,将空间中的线面求交计算转换成二维平面的线与圆弧的求交运算,在考虑刀具跳动对圆弧轨迹的影响后,求解方程组获得瞬时切屑厚度值。最后在五轴机床上进行了切削力试验,对比测量的力数据发现,仿真结果无论趋势还是大小都和实测值较好地吻合,验证了所建立的切削力预测模型的有效性。

锯形PDC齿破岩与温度特性数值模拟研究

目前关于PDC仿生齿的研究多集中在波浪齿形上,鲜有与锯形齿破岩特性相关研究的报道。鉴于此,基于弹塑性力学与Drucker-Prager岩石失效准则,建立锯形PDC齿与花岗岩相互作用的有限元模型,对锯形PDC齿的破岩以及破岩温度特性展开研究。研究结果表明:相比普通PDC齿,锯形PDC齿在破岩过程中所产生切削力峰值和均值更小,且该切削力均值减小约12.7%,机械比能减少约19%;后倾角增大情况下,锯形齿的机械比能和切削力均先减小后增大,最佳后倾角为10°时,锯形齿的机械比能和切削力最小,切削深度增加情况下,存在临界切削深度1.5 mm,超过1.5 mm后,切削力与机械比能呈现跳跃式增加,锯形齿在模拟范围内,最佳设计方案为3个锯齿。所得结论对钻头布齿和优化设计具有指导意义。

Ti-22Al-25Nb三维铣削加工切削力分析

作为一种新型材料,Ti-22Al-25Nb组织成分和结构性能研究已较为成熟,但对其加工性能方面的研究较少。利用ABAQUS/Explicit软件建立了三维铣削有限元模型,设计单因素试验和正交试验,通过极差和方差法分析不同的参数组合对切削力的影响程度。试验结果发现,切削力随着进给量和切削速度的增加而升高,但增幅较小;随着切削深度的增加切削力升高,增幅较大,影响效果明显。试验证明,对切削力的影响主次顺序为a_(p)f_(z)v。该试验为研究Ti-22Al-25Nb材料铣削工艺参数优化提供了一种方法。

考虑刀具偏心的五轴侧铣加工瞬时未变形切屑厚度模型

在五轴侧铣加工过程中,两个旋转轴运动使得刀具姿态实时变化,增加了IUCT计算的复杂程度,为保障其计算精度往往采用较为耗时的计算方法。为了解决五轴侧铣铣削中IUCT预测效率低下的问题,提出一种考虑刀具跳动的IUCT计算方法。首先建立刀具的几何模型,沿刀轴方向将刀具离散,获得当前切削点的坐标。其次,根据两个相邻刀具的位置关系推导出IUCT的显性表达式。最后,通过对比该模型和现有模型,结果表明,所提出的IUCT预测模型不仅具有良好的计算效率,同时具有较高的预测精度。

多轴加工铣削力建模与预测

为提高多轴数控加工铣削力预测精度,提出一种基于真实运动轨迹的多轴数控加工铣削力预测方法。首先采用Levenberg-Marquardt算法计算经验铣削力公式中的瞬时切削厚度,获取未变形切削厚度;然后分析多轴力变换过程中切削刃运动扫掠面和真实未变形切削厚度模型,获得基于真实未变形切削厚度的多轴数控加工铣削力预测模型;最后采用硬质合金圆柱立铣刀在五轴加工中心对2024铝合金工件进行三轴和五轴铣削实验,采集多轴数控加工铣削力数据。实验结果表明,该铣削力预测模型的预测值与实验值趋势吻合较好。

基于等效车削力及斜角切削力模型的铣削力建模

传统铣削力预测模型精度低,难以为实际生产中工艺参数的合理选择提供有效支持,建立了一种基于等效车削力模型的铣削力模型,通过综合考虑工作角度、刃口圆弧及刀尖圆弧半径的等效车削力模型。该模型将实际车刀等效为理想车刀模型识别出材料本构方程中的材料常数、流屑角及平均摩擦角,再根据斜角切削模型计算不同切削速度下的主剪切面上的剪切应力及单位切削力F0向量,从而可以计算出立铣刀前刀面上的瞬时切削力,再经过坐标变换得立铣刀在X-Y-Z坐标系下的三向切削力,仿真及实验验证了该铣削力模型的预测性。

基于材料损伤演化的钛合金螺旋铣孔切削力仿真模型

切削力仿真是降低实验验证成本、优化工艺参数的有效途径,但是螺旋铣孔为偏心加工,切削力仿真时材料损伤过程难以描述且网格畸变严重,大大局限了仿真预测的应用.通过引入物理分离准则,将断裂能演化方式定义为指数演化方式,确定断裂能参数为44350 N/m,结合加工周期内轴向和切向进给量取值范围,优化网格划分参数,最终通过ABAQUS软件实现了四齿立铣刀螺旋铣孔稳定加工阶段中单位公转周期的三维有限元模型构建.结果表明,断裂能的演化方式和网格划分参数的合理选取能够有效提高切削力仿真模型的准确性,螺旋铣孔轴向切削力和切向切削力的平均预测值为实验值的91.7%和92%,且最大误差不超过9%.模型在不同齿数(单齿、两齿、三齿、四齿)、相同几何结构立铣刀的螺旋铣孔切削力仿真中亦体现出较强的可扩展性.

基于等效刃型矢量法的钛合金螺旋铣孔切削力机械模型研究

为了准确预测钛合金螺旋铣孔过程中多齿复杂刃型专用刀具瞬时切削力的变化规律,采用等效刃型矢量法建立专用刀具的切削力机械模型。通过分析螺旋铣孔运动学特征,实现任意切削点运动轨迹的数学描述;对刀具在稳定加工阶段产生的未变形切屑与加工表面进行几何仿真分析;根据双刃切削原理,计算端刃的等效刃长及其未变形切屑的切削深度与切削宽度,同时结合侧刃的切削力分析,构建整体切削力机械模型;最后,通过试验标定切削力模型系数,实现切削力仿真值预测。结果表明,该仿真值能够准确预测专用刀具的瞬时切削力变化规律,说明等效刃型矢量法是实现螺旋铣孔切削力建模中的有效途径。

球刀铣削钛合金TC11切削力建模与分析

采用球头铣刀侧倾铣削钛合金TC11,分析了不同工艺参数对切削力的影响规律,利用非线性回归方法建立了切削力预测模型。研究结果表明,对切削力影响最显著的工艺参数是切削宽度,切削力预测模型的平均预测误差是6.28%。

基于BP神经网络的球头铣刀恒力切削控制方法研究

针对数控机床加工过程中的不可控制参数变化的问题,提出一种基于BP神经网络的球头铣刀恒力切削控制方法。分别建立铣削过程模型与BP神经网络控制模型,针对多指标变化导致恒力控制球头铣刀切削难以实施的问题,利用多层BP神经网络的自主高度拟合特性,结合恒力控制多时刻切削力与相关伺服输入,实现自适应调节多指标完成恒力控制。其中,指标包含切削力、进给量、进给速度、背吃刀量。为进一步探究噪声对控制算法鲁棒性的影响,利用方波噪声对所建立的控制算法进行干扰实验,讨论控制算法的抗干扰能力。结果表明:所提出的控制方法能够对球头铣刀控制进行快速且精确的恒力跟踪,在切削深度加深后能自适应地调整切削力;在添加噪声的恒力控制中,所获得的仿真曲线与未添加噪声时保持一致,进一步证明了该方法的抗干扰能力。该控制方法具有较好的控制性能与鲁棒性。