Tool wear detection and fault diagnosis based on cutting force monitoring

In metal cutting processes, an effective monitoring system, which depends on a suitably developed scheme or set of algorithms can maintain machine tools in good condition and delay the occurrence of tool wear. In this paper, an approach is developed for fault detection and diagnosis based on an observer model of an uncertain linear system. A robust observer is designed, using the derived uncertain linear model, to yield the necessary and key information from the system. Subsequently, it is used as a state (tool wear) estimator, and fault detection is carried out by using the observed variables and cutting force. The developed approach is applied to milling machine center. Several linear models are identified based on different working conditions. A dominant model plus uncertain terms is derived from these model set and used as an observer. Threshold values are proposed for detecting the fault of the milling machine. Examples taken from experimental tests shown that the developed approach is effective for the fault detection. The approach can be used for fault detection of failures arising from sensor or actuator malfunction.     

Investigation of the torque characteristics in vibration tapping of hardened steel

Vibration tapping is presented in this paper to solve this problem, as high-speed steel tap is incapable of tapping small-hole (M3) in hardened steel (50HRC). Theoretical analysis with fracture mechanics indicates that the impact effect of the tap on the workpiece results in increased II-type stress intensity factor and extended micro cracks, leading to lower plastic deformation, reduced cutting forces and a much lower tapping torque, and the torsional rigidity of the tap is enhanced in vibration tapping as proved by dynamic analysis. The experimental results show that with well chosen amplitudes, tapping torque decreases as vibration frequency increases, and tapping torque increases as net cutting time ratio increases, where net cutting time ratio influences the tapping torque more significantly. Vibration tapping is then proved to be a practical solution to the problem of small-hole tapping in hardened steel.     

Diagnosis of tapping process using spindle motor current

A two-stage pair-wise feature selection and classification method is proposed to diagnose the tapping process using the electrical current signal of the spindle motor. The motor current is measured with a non-intrusive Hall effect sensor. The diagnostic process is divided into two stages. In the first stage, wavelet coefficients of the current signals are computed and a subset of these coefficients is chosen as the initial diagnostic features based on their discriminatory powers for each pair of the fault classes. At the second stage, principal component analysis (PCA) is applied to reduce the dimensionality of the initial diagnostic features. Non-linear radial basis probabilistic neural networks (RPNNs) are employed for pair-wise feature classification. The final diagnostic decision is made based on a statistical voting procedure. The proposed method has been demonstrated with experimental data. On average a 93% success rate has been achieved.     

Investigation of thread tapping load characteristics through mechanistics modeling and experimentation

A mechanistic model for the prediction of tapping torque and axial force is developed. The model is capable of predicting tapping torque and axial force resulting from chip formation and tool flank/workpiece friction under various machining conditions, including dry tapping and tapping with different cutting fluids. Extensive tests on tapping torque and axial force measurements are conducted to verify the predictive model. Characteristics of the measured tapping loads are studied. It is found that the total tapping load consists of a base load and a chip packing load. The base load results from chip formation and tool/workpiece friction. The predicted tapping load is found to be in good agreement with measured base load. The chip packing load is the result of chip clogging in the flutes, and is random in nature. The chip packing load may be many times that of the base load, depending on tap geometries and the machining conditions. Factors causing severe chip clogging and excessive torque leading to tap breakage are also reported.     

基于ANN的舵机鲁棒故障检测实验研究

实验研究了基于ＡＮＮ离张学习在线检测的故障诊断方式的某实物液压舵机的鲁棒故障检测。通过提出的自适应阈值来提高故障检测系统的鲁棒性和敏感性。实验表明,该方法快速和鲁棒性地检测出舵机小幅值突变故障,早期,小幅值缓变故障。     

钝圆半径对径向中径差影响的数学模型分析

螺纹连接作为飞机中最重要承力构件,对飞机的安全性有重大的影响。所以在制造飞机的常用材料Al7075上制造出高质量的内螺纹就显得十分关键。径向中径差作为评价内螺纹质量的重要参数,对内螺纹的质量影响很大。钝圆半径会影响内螺纹的加工质量,为了研究它对Al7075攻丝加工的径向中径差影响,建立攻丝加工的准静态数学模型来进行仿真,并通过试验进行验证。结果表明：模型能够有效预测径向中径差的变化趋势;径向中径差随钝圆半径的增加呈先减小后增大的趋势,并且在10μm时获得了最小的径向中径差。     

车轴径锻生产线及径锻机现状与发展趋势

通过对车轴径锻生产线的调查研究,阐述了车轴径锻生产线的现状、径锻机在车轴自动锻造中的地位和优势以及核心设备——径锻机最新技术及发展趋势,提出了国内对径锻机及径锻生产线研究开发及投资的建议。     

液压系统故障诊断知识处理方法研究

本文针对液压系统故障诊断系统的知识处理方法及基本问题进行分析与研究,提出液压系统故障诊断知识范围,并对故障诊断知识进行合理分类,最后对液压系统的知识获取途径进行与讨论。     

径向锻机锤头磨损修复工艺研究

本文从径向锻机锤头的材料组成形式,分析了锤头磨损的不同方式。针对其磨损方式提出了不同铣削要求,使锤头表面工作层UDIMET520和中间过渡层E23-250形成了不同的焊接修复工艺,从而得到了具体的锤头修复工艺方法,提高锤头使用寿命。     

Material flow determination for radial flexible profile ring rolling

Regarding the increasing demand on annular components with complex geometries, a flexible process has been developed at the IBF to profile sleeve shaped rings. Unlike processes using grooved tools, here diverse contours can be realized on the inner surface using one “universal” tool. By extending the tool kinematics and developing an adequate forming strategy the general feasibility of the process has been shown on a bench scaled model ring rolling rig using a wax based model material. Parameters such as ring/tool geometry and roller feed strategy were detected as having an effect on material flow resistance in the rolling and transverse directions. Expressing them by geometric ratios, the material flow distribution could be determined in numerous experiments and quantified by a newly-defined extension coefficient with a certainty of 95%. This achievement enables us to predict the material flow in axial and tangential directions to manufacture complex geometries reproducibly.     

浅谈径锻机模具对产品的影响

通过对现场产品的研究发现,径锻机的夹爪和锤头对于整个径锻工艺有很重要的作用。通过对夹爪和锤头的理论分析,了解模具对产品可能产生的影响,通过合理的模具设计,工艺编排规避不良影响,使产品尺寸精准度更高,表面质量更佳。     

径向挤压的金属流动分析

以十字轴的径向挤压为例，较为详细地论述了径向挤压的流动规律，这些流动规律为径向挤压件工艺方案的制定和径向挤压件的有限元分析提供了实验依据。     

基于故障树的数控机床故障诊断算法设计的研究

根据故障树分析法的具体理论基础,以数控机床急停实例分析了算法流程;设计了递归算法、基于BDD图求解MCS算法及模块化分解算法;并进行了故障树相关的定量分析,为基于故障树的数控机床故障诊断奠定了基础。     

主轴径向跳动数字化测量仪表的设计

为了解决指针式仪表在主轴径向跳动测量中无法提供标准电流信号的困难,提出在传统的机械测量机构嵌入一个滑动可变的精密电阻,通过电桥回路将电阻变化量转换成电压信号,利用运算放大器对其电阻值进行线性化处理,从而形成符合国际标准的接口信号,由此建立一个由基础测量、数据处理和实时监控组成的三层网络系统.该网络的功能旨在实现远程数据采集、信号传输、数值计算、图像处理等.将新设计的仪表与标准光栅进行数据比对实验显示,采用特殊修刻工艺制作的可变电阻输出值与线性机械位移量之间可以呈现严格的对应关系,从而为该仪器的实验室研究走向与再制造有关的实际应用奠定基础.研究结果表明:与传统方法相比,新方法更加注重采集大量的数据,形成合适的样本集合并建立对应的数学模型.通过构造的曲线与观测点的拟合情况来进一步优化模型,并对今后的变化趋势进行预测,这样可以检测出隐匿很深的内部缺陷,从而为指导维修工作提供有价值的参考信息.     

Generic modelling of milling forces for CAD/CAM applications

CAD/CAM systems need technical data to quantitatively predict the performance of the milling process. The great varieties of real machining operations prevent exhaustive studies for each machining condition. The purpose of this paper is to present a generic approach of the milling forces modelling. The objective is to limit the experiment testing while providing accurate enough data for the CAD/CAM requirement. An experimental study is presented to analyse the major influent parameters (rake angle, cutting speed) on the cutting forces. Then, simulation results based on a modified Altan’s approach are compared with experimental measurement for two different steels (AISI H11 and P20) and varying insert geometries to value the predictive capability of the presented approach.     

Optimal ultrasonic pulse repetition rate for damage detection in plates using neural networks

An experimental study for the determination of the optimal pulse repetition rate frequency (PRF) for damage detection in aluminum and composites is presented in this paper. A method for predicting the damage size and depth from C-Scan results using neural networks is also presented. Two graphite fiber IM7/F5250-4 (Bismaleimid) composite plates and four aluminum plates were used for the study. Damage was fabricated by drilling holes of varying depth and diameter on the test specimens. Ultrasonic transmission tests were carried out on a DIGITALWAVE immersion type C-Scan system. PRF values from 100 to 5000 Hz were investigated for the scan. The defect locations were clearly observed as peaks in the C-Scan mesh. The equivalent hole diameter, depth and the location of the holes with respect to a predetermined edge were calculated from the C-Scan plots and correlated with the actual values to determine the optimal PRF values. A close correlation was found between the calculated diameter obtained from the C-Scan results and the actual hole diameter. Low PRF values (100 Hz) were found best for scanning of aluminum and intermediate values (500 Hz) were best for scanning of composites. Prediction of the actual damage size from the C-Scan calculated damage size was successfully accomplished with radial basis function neural network.     

Specific machining forces and resultant force vectors for machining of reinforced plastics

When machining fiber reinforced plastics, the machining forces may induce workpiece damage if they exceed the workpiece's anisotropic strength values. Knowledge of the resultant force vectors is therefore important to allow optimization of tool geometry and machining strategy. This article deals with experimentally obtained machining forces on short glass fiber reinforced polyester. Specific cutting, passive and axial forces have been determined for varied parameters of cutting velocity, cutting depth, cutting edge rounding and tool inclination. Generic multivariate regression models have been calculated, which, implemented in a kinematic simulation, allow calculation of machining forces (and direction) for arbitrary milling operations.     

烧结金刚石串珠绳锯切花岗石的锯切力研究

本文对烧结金刚石串珠绳在锯切花岗石过程中,锯切力及锯切后工件表面的轮廓进行了跟踪检测,研究了锯切过程中,锯切力随锯切参数的变化,以及锯切力与工件表面轮廓的相互关系。实验结果表明：锯切过程中,工件上所承受的锯切力Fh和Fv随着线速度Vs的提高而减低,随着进给速度吩的提高而增加。垂直力与水平力之间存在着良好的对应关系,垂直力与水平力比约为4．18。加工后工件轮廓偏差量随着工件所承受的垂直力的增加而增加,两者之间呈指数关系。     

金刚石绳锯切割混凝土的锯切力实验研究

对烧结金刚石串珠绳锯在锯切混凝土过程中锯切力的变化进行了跟踪检测实验,研究了锯切力随锯切参数及锯切长度的变化规律.实验结果表明:锯切过程中,工件上所承受的锯切力(水平力Fh和垂直力Fv)随着线速度vs的提高而减低,随着进给速度vf的提高而增加.锯切力随着锯切中工件长度L的增加而增加.垂直力与水平力之间存在着良好的对应关...     

径向磁轴承柱槽比优化分析

本文建立了以径向磁轴承最大载承力Fmax为目标，在临界温升τ等多约束条件下，对定子柱槽比k的优化模型，设计变量选取轴承静态气隙s0和定子柱槽比k，采用模糊优化算法，计算结果表明，在其它参数不变的条件下，轴承静态气隙s0和定子柱槽比k在一定的取值范围内，对最大承载力Fmax有规律性影响，达当减小轴承静态气隙s0和增大定子柱槽比k都能显著提高轴承最大承载能力Fmax，结合试验结果对灵敏度进行了分析，并给出了相应结合。