EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.     

EFFECTS OF COOLANT SUPPLY METHODS AND CUTTING CONDITIONS ON TOOL LIFE IN END MILLING TITANIUM ALLOY

Titanium machining poses a great challenge to cutting tools due to its severe negative influence on tool life primarily due to high temperature generated and strong adhesion in the cutting area. Thus, various coolant supply methods are widely used to improve the machining process. On account of this, tool life and cutting force are investigated based on dry cutting, flood cooling, and minimum quantity lubrication (MQL) techniques. The experimental results show that MQL machining can remarkably and reliably improve tool life, and reduce cutting force due to the better lubrication and cooling effect.     

刀具材料的历史、进展与展望

论述了刀具和刀具材料在人类历史发展中所起的重要作用。回顾了早期机械制造中曾经用过的刀具材料。重点阐述了现代刀具材料(高速钢、硬质合金、陶瓷、超硬材料)的化学成分、制造方法、切削性能和应用范围。对21世纪中刀具材料的发展动向也作出了预测与展望。     

难加工材料型腔圆角数控铣削的切削力预测

在难加工材料型腔的数控铣削过程中,圆角区域的加工阶段,径向切削深度和真实进给量的变化很大程度上影响切削力,造成扎刀、撞刀、振动等很多的问题, 影响工件的加工准确度和刀具的寿命,甚至使得加工无法顺利进行.文中建立端铣刀和圆角轮廓几何关系的数学模型,提出普遍适用于矩形与梯形型腔圆角的切削力预测方法.最后,对型腔圆角切削力的变化规律预测方法进行验证.     

高速铣削航空铝合金7050-T7451时刀具的磨损破损

分析涂层硬质合金刀具高速铣削航空铝合金7050-T7451时的磨损、破损形态,通过正交试验研究了高速铣削航空铝合金的铣削力及其变化规律,提出模拟高速铣削刀具裂纹萌生的脉冲激光热冲击试验方法,研究铣削力和热应力在刀具磨损、破损过程中的不同作用.试验和理论分析证明:高速铣削航空铝合金7050-T7451时,热应力使刀具萌生裂纹,裂纹在热应力和机械应力综合作用下扩展.研究刀具失效机理,证明:高速铣削航空铝合金时,粘结磨损和扩散磨损是主要磨损机理.提出通过提高切削系统稳定性和优化切削参数,可以有效降低机械应力对刀具的冲击作用,并在生产现场收到良好的效果.     

三维有限元分析在高速铣削温度研究中应用

高速切削过程中切削温度对刀具磨损、工件加工表面完整性及加工精度有极大的影响。应用有限元法对高速铣削铝合金薄壁件过程中工件与刀具接触面温度、工件内部的温度分布进行了仿真研究,仿真过程中考虑了切削速度、进给量对切削温度的影响。通过红外热像仪对不同主轴转速下工件表面温度的测量,验证了仿真结果与试验结果比较接近。得出在高速切削铝合金过程中,随着切削速度的增加,刀具与工件接触区的温度变化存在二次效应。该结论对铝合金薄壁件加工具有重要的实用价值。     

Detection process approach of tool wear in high speed milling

The cutting tool wear degrades the quality of the product in the manufacturing process, for this reason an on-line monitoring of the cutting tool wear level is very necessary to prevent any deterioration. Unfortunately there is no direct manner to measure the cutting tool wear on-line. Consequently we must adopt an indirect method where wear will be estimated from the measurement of one or more physical parameters appearing during the machining process such as the cutting force, the vibrations, or the acoustic emission, etc. The main objective of this work is to establish a relationship between the acquired signals variation and the tool wear in high speed milling process; so an experimental setup was carried out using a horizontal high speed milling machine. Thus, the cutting forces were measured by means of a dynamometer whereas; the tool wear was measured in an off-line manner using a binocular microscope. Furthermore, we analysed cutting force signatures during milling operation throughout the tool life. This analysis was based on both temporal and frequential signal processing techniques in order to extract the relevant indicators of cutting tool state. Our results have shown that the variation of the variance and the first harmonic amplitudes were linked to the flank wear evolution. These parameters show the best behavior of the tool wear state while providing relevant information of this later.     

基于进化神经网络的电火花铣削加工电极损耗预测

针对电火花铣削加工的时变非线性特性,提出基于神经网络的电火花铣削加工电极损耗预测模型,利用该网络预测加工速度和工具的相对损耗,从而可在加工中实时计算出工具实际损耗量,为实现电极损耗的在线动态补偿打下基础。针对神经网络传统训练算法-BP算法的不足,提出了一种自适应调节变异率和变异量的进化算法来优化网络权值和网络结构,提高了网络的逼近精度和进化速度。     

进给方向毛刺抑制技术的研究

在对金属切削中进给方向毛刺生成机理进行试验研究和理论分析的基础上，给出了表示产生Ⅰ型微小进给方向毛刺的重要物理量──刀具临界主偏角β_（ｒＩ）。讨论了有关主要因素对临界主偏角的影响，进而开发出了几种抑制或减小进给方向毛刺的新工艺和新方法。     

STUDY ON THE CUTTING TEMPERATURE IN GEAR HOBBING

０ＩＮＴＲＯＤＵＣＴＩＯＮＧｅａｒｈｏｂｂｉｎｇｉｓａｍａｉｎｐｒｏｃｅｄｕｒｅｍｅｔｈｏｄｆｏｒｔｈｅｒｏｕｇｈｉｎｇｃｕｔｏｆａｕｔｏｍｏｂｉｌｅｇｅａｒｓ．Ｈｏｗｔｏｒａｉｓｅｔｈｅｌｉｆｅｏｆｇｅａｒｈｏｂｓａｎｄｔｈｅｅｆｉｃｉｅｎｃｙｏｆ...     

高温自润滑陶瓷刀具材料及其切削性能的研究

以TiB2为添加剂,Al2O3为基体,制备了Al2O3/TiB2陶瓷刀具材料。以该陶瓷刀具对淬硬钢进行高速干切削试验,利用其在切削高温作用下的摩擦化学反应,在刀具材料表面原位生成具有润滑作用的反应膜,从而实现Al2O3/TiB2陶瓷刀具材料本身的高温自润滑。研究了Al2O3/TiB2陶瓷刀具在切削高温作用下刀具表面的摩擦化学反应机理,分析了刀具表面自润滑膜的组成结构。结果表明：Al2O3/TiB2陶瓷刀具在干切削淬硬钢时,当切削速度大于120 m/min时,开始表现出高温自润滑性能。自润滑膜的组成为Al2O3/TiB2陶瓷刀具中TiB2的氧化产物,它能在刀具表面起到固体润滑剂的作用,进而降低前刀面的摩擦因数,减轻刀具的粘着磨损,提高刀具的耐磨性能,具有良好的减摩和抗磨作用。     

Novel tool wear monitoring method in ultra-precision raster milling using cutting chips

Tool wear monitoring is a popular research topic in the field of ultra-precision machining. However, there appears to have been no research on the monitoring of tool wear in ultra-precision raster milling (UPRM) by using cutting chips. In the present research, monitoring tool wear was firstly conducted in UPRM by using cutting chips. During the cutting process, the fracture wear of the diamond tool is directly imprinted on the cutting chip surface as a group of ‘ridges’. Through inspection of the locations, cross-sectional shape of these ridges by a 3D scanning electron microscope, the virtual cutting edge of the diamond tool under fracture wear is built up. A mathematical model was established to predict the virtual cutting edge with two geometric elements: semi-circle and isosceles triangle used to approximate the cross-sectional shape of ridges. Since the theoretical prediction of cutting edge profile concurs with the inspected one, the proposed tool wear monitoring method is found to be effective.     

Life prediction system using a tool’s geometric shape for high-speed milling

In recent years, machinery and tool technology has been developing rapidly. The accuracy of operations have also become more and more exact. Elsewhere, raw materials have also been honed, hoping to provide more useful properties than previously. Thus, how to find the best way to prolong the life of a tool subjected to hardened material cutting is the target of this research. Three kinds of tool angle of the endmill are used in this research; clearance angle, rake angle, and helical angle. The cutting conditions are the same; we only change the tool angle for all the cases studied. We attempt to discover better tool geometrical angles for the high-speed milling of NAK80 mold steel. The tool wear rate was measured through a toolmaker’s microscope and the roughness of the machined surface was measured by the roughness-measuring instruments after several complete surface layers were removed from the workpiece in the experiment. Also, a noise-mediator was used to detect the level of cutting noise during each surface layer workpiece removal of the high-speed milling process, and different noise levels were then compared with the tool wear rates for identifying noise characteristics in the case of an over-worn tool state. An abductive network was applied to synthesize the data sets measured from the experiments and the prediction models are established for tool-life estimation and over-worn situation alert under various combinations of different tool geometrical angles. Through the identification of tool wear and its related cutting noise, we hope to consequently construct an automatic tool wear monitoring system by noise detection during a high-speed cutting process to judge whether the tool is still good or not, and, so, the cost of milling can be reduced.     

基于正交试验的铣削振动影响因素分析

切削振动对零件加工表面质量影响较大,为了控制切削振动,提高加工表面质量,利用正交试验进行不同工艺条件下的铣削试验,采集振动信号并提取信号特征值,通过方差分析等方法研究铣削参数和刀具磨损对铣削振动的影响规律,确定影响铣削振动的显著因素,为切削振动控制研究及铣削工艺参数的合理选择提供理论参考。     

基于切削力实现铣刀状态监测的特征值选取的研究

对于采用单一切削力传感器实现刀具状态监测,进行了实验研究.分别对切削力信号进行了时域分析和小波分析,选取了合理的监测特征.对于单一传感器无法实现高精度监测的问题,提出了多传感器融合的方法,实验与仿真结果验证了可行性.     

CHIP MORPHOLOGY CHARACTERIZATION AND MODELING IN MACHINING HARDENED 52100 STEELS

Hard machining is attracting more and more attention as an alternative to grinding in finish machining some hardened steels. The saw-toothed chips formed in hard machining have their own unique characteristics. The saw-toothed chip morphology is of great interest since the understanding of the saw-toothed chip morphology and its evolution in machining helps unveil hard machining chip formation mechanisms as well as facilitate hard machining implementation into industry. In this study, the effect of tool wear and cutting conditions on the saw-toothed chip morphology was examined in machining 52100 hardened 52100 bearing steel. It was found that the chip dimensional values and segmentation frequency were affected by tool wear and cutting conditions while the chip segmentation angles were approximately constant under different tool wear and cutting conditions. The shear band spacing has also been predicted at the same order of magnitude as the measurement, and improved spacing modeling accuracy is expected if the cutting process information can be better predicted first.     

CHIP MORPHOLOGY CHARACTERIZATION AND MODELING IN MACHINING HARDENED 52100 STEELS

Hard machining is attracting more and more attention as an alternative to grinding in finish machining some hardened steels. The saw-toothed chips formed in hard machining have their own unique characteristics. The saw-toothed chip morphology is of great interest since the understanding of the saw-toothed chip morphology and its evolution in machining helps unveil hard machining chip formation mechanisms as well as facilitate hard machining implementation into industry. In this study, the effect of tool wear and cutting conditions on the saw-toothed chip morphology was examined in machining 52100 hardened 52100 bearing steel. It was found that the chip dimensional values and segmentation frequency were affected by tool wear and cutting conditions while the chip segmentation angles were approximately constant under different tool wear and cutting conditions. The shear band spacing has also been predicted at the same order of magnitude as the measurement, and improved spacing modeling accuracy is expected if the cutting process information can be better predicted first.     

刀具切削状态的电机电流监测新方法

本文从实时在线监测刀具切削状态的应用出发,研制了一种新型的电机电流拾取方法和传感装置,并分析了刀具在加工过程中切削力,电机电流与刀具切削状态的关系,同时,研究了利用电机电流信号进行刀具切削状态的监测原理,实验证明了其方法的可靠性和实用性。     

多传感器刀具状态监控系统

介绍一个多传感器、多特征量的刀具状态监控系统。以声发射、功率监控和改进的神经网络技术,借助刀具监控软件,识别刀具切削工作的正常和失效状态。软件有信号采集、特征提取、网络训练回忆以及监控等功能,可实现离线和在线监控。并以离线控制试验为实例,考核该系统识别刀具状态的可靠性。     

SPDT超精密切削时切削变形与切削力的研究

研究了超精密切削时，单晶金刚石刀具与工件间的摩擦系数、刀具锋锐度、切削厚度等对切削变形系数、切削力及加工表面质量的影响。作者认为在超精密切削时，要提烹加工表面质量，优选金刚石刀具的晶面方向、提高金刚石刀具的锋锐度是十分重要的，在超精密切削单晶材料时，工件晶面的选择也是十分重要的。