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.

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.

The Design of Form Milling Cutter as the Curve of the Back of Tooth Is Logarithmic Spiral

Form milling cutter is built-for-purpose cutter which process the form surface, for example, usually process male and female circular arc face and form trench and so on. From the traditional concept, form milling cutter is divided into pointed tooth and relieving follow its structure. Relieving shaped cutter is more convenient than pointed tooth milling cutter, because only its rake face is needed to grind after it turn into blunting, so the current books which are used in college almost select relieving shaped cutter in order to introduce how to design the form milling cutter.The curve of the back of tooth of relieving cutter is the transversal which is formed by the rear face of tooth in the end cut plane of the milling cutter. In the past, because of the limit of the manufacturing technology, the curve of the back of tooth is often selected Archimedes’ curve, in order that the shovel-nose tool acquire the uniform motion when the cutter shovel the back, in other word, the rear face of the milling cutter rotate its axis by the new cutting lip, in the same time, it move uniformly to the axis in order to form the surface. Although this curve of the back of tooth meet the fixedness of the form of blade around grinding the cutter, the rear angle of the dot of the cutting lip don’t keep fixedness. With the development of the modern manufacturing technology, the unmanageable problem of many complex curves is already easily solved. So it is need to study the optimum profile of the curve of the back of tooth in theory, and study the design theory of the relieving shaped cutter under the condition of new manufacture, in order to ensure that the rear angle of the dot of the cutting lip keep fixedness after the relieving shaped cutter is grinded. The paper derive the curve profile of tooth of the form cutter and the modifier calculation formula of the profile of the cutter edge from the definition of the rear angle of the cutter, which establish the foundation for the precision design and manufacture of other form cutter.

MATHEMATICAL MODEL OF NC MACHINING NONCONVENTIONAL MILLING CUTTERS-FORMING METHOD OF RAKE FACES

How to generate rake faces of nonconventional milling cutters (NCMC) with constant spiral angled and normal rake angled edges on NC machine tools is presented by use of a blunt cup grinder or a cup milling cutter. Motion functions of the NC machining system are mathematically deduced and exam- ed by a experiment. The research will provide theoretical and practical guidance for machining noncon- ventional tools on NC machine tools.

CUTTING TEMPERATURE MEASUREMENT IN HIGH-SPEED END MILLING

A computer aided measurement system is used to measure the cutting temperature directly in high-speed machining by natural thermocouples and standard thermocouples. In this system the tool/workpiece interface temperature is measured by the tool/workpiece natural thermocouple, while the temperature distribution on the workpiece surface and that of interior are measured by some standard thermocouples prearranged at proper positions. The system can be used to measure cutting temperature in the machining with the rotary cutting tools, such as vertical drill and end milling cutter. It is practically used for the research on high-speed milling with hardened steel.

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.

Influence of Helix Angle on Stability of Milling Flexible Parts

Geometry of end mill cutters plays a vital role in the stability of the flexible parts milling.The present study considers helix angle and number of flutes.Multi-frequency solution is established to draw stability Lobe diagram(SLD)for different helix angles and number of flutes.SLD for the two cases shows that the greater the value of helix angle,the more stable the milling process will be,and conversely increasing the number of flutes degrades the stability of flexible parts milling.A simple empirical methodology is adopted to employ the inclined plane workpiece geometry offering agradual increase of the axial depth of cut in the feed direction.Surface roughness is used as a measure of stability.Test results corroborate the model conclusions very well.

A simplified method for local tool interference detection and tool position modification during five-axis ball-end milling process

Five-axis ball-end milling is commonly used to machine the complex surfaces. Local tool interference phenomenon which often occurs in five-axis milling should be urgently solved. In this paper, a simplified method to detect the occurrence of local tool interference and modify tool position is proposed. First, the detection matrix is established to detect local tool interference at all the cutter location points on tool path simultaneously in five-axis ball-end milling of complex surfaces. The algorithm of detection matrix based on point arithmetic is simple. Secondly, the new coordinates of the modified interfering-free points are obtained precisely by using the genetic algorithm. The feasibility of the method is validated by simulation in Matlab. This research is benefit to simplify the calculation of local tool interference detection and tool position modification.

Research on Machined Surface Veins Based on Turn-milling Technology

Turn-milling which history dates from the end of the 20th century is one of the advanced metal cutting technologies. It could precisely machine hard materials as an alternative to turning for certain limitations. A series of orthogonal turn-milling surface veins experiments have been done on the turn-milling machining center by machining aluminum alloy,and then the nexus between the surface veins and the cutting regimes is studied. The mathematical model for surface vein direction angle is established,also the forming mechanics of surface vein direction is analyzed. Its variety regulation presents decreasing trend with as axial feed and cutter rotary speed increasing. For different eccentric distance of orthogonal turn-milling,the surface veins are different.

铣削高温合金GH3039刀具寿命预测及磨损机理

为揭示高温合金GH3039铣削参数对刀具寿命的影响规律,采用正交试验法对其进行铣削试验,运用多元回归法建立刀具寿命预测模型,分析铣削参数对刀具寿命的影响规律,通过观测铣刀后刀面的磨损情况,探究不同主轴转速下铣刀的磨损机理。结果表明:主轴转速对刀具寿命的影响程度最大,最小为轴向切深;当主轴转速为750 r/min时,铣刀磨损区域主要以黏结磨损和磨粒磨损为主;当铣削速度为950 r/min时,氧化磨损与扩散磨损开始增强;当铣削速度为1 180 r/min时,磨粒磨损与黏结磨损开始减弱甚至消失,氧化磨损与扩散磨损占据主导地位。

具有内阻的旋转锥形复合材料刀杆铣削过程稳定性的仿真分析

研究考虑材料内阻的旋转圆锥形复合材料刀杆铣削系统的再生颤振稳定性。基于复合材料粘弹性本构关系、Hamilton原理和Rayleigh梁理论,结合再生时滞铣削力模型,分别导出旋转坐标以及惯性坐标表示的颤振偏微分方程。采用Galerkin法对颤振偏微分方程进行离散化。基于自由振动分析和能量法计算复合材料刀杆的模态损耗因子;基于特征值分析技术计算旋转复合材料刀杆的临界速度和失稳阈。采用时域半离散法和频域零阶近似解法,预测切削系统的稳定性。分析锥度比、长径比、铺层角、铺层方式,以及内、外阻对切削稳定性的影响。计算结果表明,轴对称旋转刀杆铣削过程在两种坐标系下的稳定性预测结果是一致的。研究发现,在高转速下,由于旋转复合材料刀杆内阻的作用,切削系统出现新的不稳定区域。这些新的不稳定区域的起始转速等于旋转复合材料刀杆的失稳阈。

PCD刀具超声振动辅助铣削TC4钛合金仿真与试验

TC4钛合金是典型的难加工材料,为解决其导热性差对铣削加工性能的影响,文章提出超声振动辅助铣削加工工艺,以提高其铣削质量。通过Abaqus建立PCD铣刀及TC4钛合金工件的仿真模型,分析超声振动对PCD铣刀切削刃温度的影响;采用单因素法设计超声振动铣削试验,研究不同超声振幅与刀具前角对PCD铣刀切削刃温度、铣削力及工件表面粗糙度的影响;并将试验结果与仿真结果进行对比,验证仿真模型的可靠性。结果表明,超声辅助铣削可大幅降低切削刃温度和铣削力,还可有效降低工件表面的粗糙度。相较普通铣削,超声铣削的切削刃平均温度由421.5℃下降到241.9℃,降幅为42.6%;铣削力由104.65 N下降到87.05 N,降幅为16.8%;工件表面粗糙度均值由0.316μm下降到0.228μm,降幅为27.8%。超声振幅较铣刀前角对表面粗糙度的影响更明显,且仿真结果和试验结果基本一致,其平均误差为4.6%。

双圆弧斜齿齿轮泵转子加工刀轨规划及仿真

针对双圆弧斜齿齿轮泵转子加工方法中存在的加工效率和精度比较低等问题,提出了利用球头铣刀在数控铣床上加工双圆弧斜齿齿轮泵转子的方法。研究目标是:根据双圆弧斜齿齿轮泵转子方程,结合空间啮合原理,建立了双圆弧斜齿轮的加工坐标系,根据各坐标系之间的转换矩阵,建立了双圆弧斜齿齿轮泵转子的齿面方程,模拟使用球头铣刀进行加工过程,计算出加工刀具中心在平面和空间轨迹,同时给出判定球头铣刀不发生干涉的最大半径的方法。利用VERICUT软件建立虚拟制造环境并进行铣齿仿真加工,验证了双圆弧斜齿齿轮泵转子齿面数控加工方法的正确性及其可行性。

硬质合金涂层刀具铣削堆焊合金试验研究

对试验堆焊合金合理加工参数与涂层刀具磨损机制进行了分析。采用逆变直流焊机与特制的含稀土药皮耐磨堆焊焊条在试板表面进行堆焊焊接,采用数控铣床分组加工试验堆焊合金,分别对堆焊层进行了成分检测与金相组织分析,对试验用APMT1604PDER型硬质合金涂层刀具进行了金相分析、电镜形貌观测以及能谱分析,研究了不同参数及加工量条件下刀具涂层与内部基体铣削表面特征以及磨损分析。数控铣床采用4齿刀盘时,相同每齿进给量试验堆焊合金材料的合理加工参数为Vc:0.085r/min,ft:≤0.05mm/min,ap:≤0.2mm。试验刀具的表面涂层为AlTiN类型,刀具基体材料主要为500nm~2μm不规则碳化钴、碳化钨合金粉末组成;试验刀具的失效形式:初期为磨粒磨损,中期与后期以黏结磨损与扩散磨损为主。

整体式木工硬质合金立铣刀铣削温度仿真分析

以整体式木工硬质合金立铣刀铣削刨花板时铣刀温度分布为研究对象,探究铣削深度、前角、及螺旋角对铣刀温度的影响规律,并通过优化参数提升铣削过程的效率和稳定性。采用动力学仿真分析模拟实际切削工况,对立铣刀铣削温度进行理论分析,得出铣削深度、前角、螺旋角三个主要研究变量。通过Abaqus软件分析以及试验探究,分析以上三个研究变量对立铣刀铣削刨花板过程中刀刃温度变化的影响,验证了立铣刀铣削温度模型的可行性。铣削过程中,铣刀的温度经历快速上涨、缓慢上升、趋于稳定三个阶段。其他条件一定,当切削深度为4.0 mm,前角为17°,螺旋角为22°时,刀刃的平均温度较低。研究结果对立铣刀铣削加工温度的深入研究具有重要的理论和实践意义。

基于SYSWELD的等高齿弧锥齿轮铣刀盘多层焊接数值模拟

本文借助Visual-Environment焊接模拟仿真软件,以SYSWELD为求解器对等高齿弧锥齿轮铣刀盘V形坡口多层焊接的焊接温度场进行数值模拟,得到了焊接温度场分布云图,分析并对比了每层焊缝中心、焊趾及距焊缝中心5mm处的温度循环曲线,推导出三层焊接温度场公式用于计算验证。结果表明,熔池中心温度最高,距离焊缝中心越近,温度梯度变化越大。

基于改进LSTM-AdaBoost的铣刀磨损量预测

针对铣刀磨损量预测时精度低的问题,提出一种基于黑寡妇算法(BWO)优化的长短期记忆神经网络(LSTM)与AdaBoost集成学习算法相结合的铣刀磨损量预测方法。在铣刀磨损振动信号中提取时域、频域以及时频域多域特征。通过BWO算法优化LSTM的核心参数,并将优化后的LSTM网络与AdaBoost算法进行结合,构建铣刀磨损量预测模型。最后用PHM Society 2010铣刀全寿命周期的振动数据进行实验。研究结果表明:所提方法能够有效地预测出铣刀磨损量变化值,优化后模型的平均绝对误差百分比为3.436%、均方根误差为6.471、决定系数R^(2)为0.935。该方法能够获得准确率更高的铣刀磨损量预测值,预测效率更高。

锥度球头刀加工钛合金TC4表面粗糙度建模

高性能商用航空发动机大型复合材料风扇叶片高速旋转时存在分层开胶风险,需要在其前缘通过胶结工艺装配钛合金TC4前缘金属加强边予以保护,而胶结性能受到装配表面粗糙度影响较大。本文针对钛合金TC4前缘金属加强边内腔加工表面粗糙度,以主轴转速、每齿进给量和轴向切深为设计因子,分别开展4种细长锥度球头刀四轴铣削钛合金TC4试验,测试已加工表面粗糙度。基于测试的样本数据,分别针对4种细长锥度球头刀建立加工表面粗糙度的经验模型。结果表明,主轴转速增加,直径为5.0mm时,表面粗糙度大幅降低,直径为3.0mm时,表面粗糙度却有所增加;主轴转速、每齿进给量增加时,直径4.0mm、2.4mm的锥度球头刀加工的表面粗糙度没有较大变化。随着轴向切深增加,4种直径的刀具加工的表面粗糙度均大幅增加。

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。

兼顾排屑与降载作用的叶轮拐角单笔清根刀具

清根加工作为叶轮拐角区域残余材料的补加工工艺,在整体叶轮数控加工中占据十分重要的地位。盖盘叶轮清根加工具有推刀进给、拐角曲面曲率大、切削余量大、空间几何受限等特点。而传统球头铣刀刀尖点切削性能不足,应用于盖盘叶轮清根加工会导致切削载荷大和切屑挤压,造成刀具过早失效、加工表面质量差等问题。本文针对盖盘叶轮清根加工的特点和难点,提出一种面向不同拐角尺寸的具有削顶结构以及大容屑槽结构的刀具,并推导了切削刃的表达式。对传统球头铣刀和新式削顶铣刀进行仿真与实验,结果表明,新式削顶铣刀较传统球头铣刀切削力降载高达77.6%,切削过程更平稳可靠,加工质量更高。