玻璃纤维机加工刀具失效的在线监测准则

玻璃纤维增强聚合物复合材料(GFRP)由于其特殊的材料属性被广泛应用于轻型结构中,然而其加工过程会发生刀具过度磨损,直接影响了加工工件材料的完整性。基于此,提出了一种GFRP材料加工过程中刀具磨损失效的在线监测准则,对刀具失效时的振动信号和主轴功率信号进行了采集,开展了刀具和工件的切削试验,对测量的振动信号进行分析,对该监测准则进行了试验验证。进一步建立了刀具颤振监测准则,从颤振信号分析了刀具的失效,并通过试验验证了该准则的可行性。     

无先验知识下基于CHMM的刀具磨损监测技术

切削刀具的状态直接影响工件加工质量、生产率和产品成本,因此在切削加工过程中监测刀具的状态显得尤为重要。针对实际监测系统通常无法获取刀具各磨损退化状态先验知识的情况,以切削力与切削振动为监测信号,提出无先验知识下基于小波包分析与连续隐马尔可夫模型的刀具磨损监测技术。应用小波包分析技术提取信号特征信息,采用S函数实现特征值归一化处理。利用监测过程中的刀具正常状态下归一化特征信息建立基于连续隐马尔可夫模型的监测模型;根据刀具未知状态特性向量与监测模型间的对数似然度获取刀具性能指标PV,实现刀具磨损状态评价。采用铣刀磨损全寿命数据来验证该方法的有效性,实验结果表明:该方法能在无先验知识的情况下对刀具的健康状态进行较为准确的评估,且所需样本数较少,训练速度快。该技术对实现无先验知识下的刀具智能化在线状态监测具有重要意义。     

刀具实时健康监测系统研究

为保证加工过程中工件加工质量,降低废品率,须实时监测刀具的健康状态。分析了刀具声发射检测机理,设计了一非接触式光纤F-P传感器,建立基于光纤声发射技术的刀具实时监测系统,利用虚拟仪器技术开发了切削加工过程中刀具监测的声发射信号采集和报警软件,进行了实验研究。结果表明,该系统能有效实现刀具切削过程中状态变化的非接触监测,系统软件界面友好,操作简单,具有一定的灵活性,易于扩展功能,可靠性高,成本低。     

基于小波-神经网络纹理图像识别的刀具状态监测

介绍了一种采集旋转工件图像的光学监测系统,提出通过二维小波分析工件纹理图像,提取纹理特征,设计了基于动态和静态神经网络的刀具状态识别系统,该系统可用于自动化加工中刀具诊断,仿真证明了有效性。     

基于DEFORM的刀具几何参数与切削力关系的研究

切削力是切削过程中重要的参数之一,它对工件的加工精度、加工所消耗的功率及刀具的磨损程度等方面都有着重要的影响。影响切削力的因素是多方面的,如工件材料的性能、刀具的几何参数、切削用量的影响、切削液的使用情况等等[1]。文章以镍基合金为切削载体、以DEFORM为仿真平台,建立切削仿真模型,研究了刀具角度对切削力的影响,仿真结果与实际切削过程一致,验证了仿真的有效性,从而为研究者提供了一种实验成本低、实验时间短的方法来确定切削刀具工作角度。     

成本低廉的智能刀柄传感器系统

在切削加工过程中，为了有效地跟踪刀具磨损、监测刀具径跳和预测次生颤振的发生，从而能在工件损坏之前提前调整切削参数，在刀具的刀尖处直接观测刀具的响应特性是非常有用的。为了以较低的成本实现这一目标，     

用预断力模型建模和模拟铣削中的颤震

为模拟和分析铣削过程中的颤震,介绍了一种预断时域颤震模型.开发的模型使用了预断铣削力模型,该模型描述了多刃同时加工时铣刀的工作状态,并由主要工作材料性质、刀具几何和切削条件,预断铣削力.瞬时未变形切屑厚度被建模,包括了刀具振动引起的动态调制,使动态再生效应被考虑进去.为精确求解,使用了Runge-Kutta法求解微分方程,决定铣削系统的动态特性.使用预断模型,开发了铣削颤震窗口显示模拟系统,由输入刀具和工件材料性质、刀具参数、机床特性和切削条件,以数值和图示两种格式,用刀具-工件位移和相对于刀具转动的切削力变化,表示出预断的颤震.用试验结果验证了该系统,并显示出良好的一致性.     

薄壁筒车削颤振稳定性预测

切削颤振是制约薄壁筒工件加工质量和效率的主要因素之一。采用半离散法对含有时滞项的动力学方程进行稳定性预测分析,结合薄壁筒工件切削振动试验,研究刀具、工件动力学参数匹配关系变化对切削加工稳定性的影响。通过仿真分析得出:随着刀具刚度或固有频率的提升,切削系统稳定性呈上升趋势,但过度提升刀具刚度并不会有效提升切削稳定性;在刀具与工件固有频率接近处,切削系统的稳定性较差;适当调整刀具动态特性参数有利于提高柔性工件切削加工的稳定性;切削过程中,时变的切削位置和工件尺寸会引起切削系统动态特性的变化。根据时变稳定性预测图,从稳定性分析角度解释了一次走刀切削试验中薄壁筒工件表面出现不同加工形貌的原因。     

五轴球头铣削加工表面三维形貌分析

基于五轴球头铣削加工过程中刀具偏离对工件表面形貌产生的影响,提出一种五轴球头铣削加工表面形貌预测和粗糙度分析模型。该模型结合铣削工艺参数如切削槽数量、进给速度、切削深度以及偏心率和刀具径向跳动产生的影响对表面形貌和粗糙度参数质量(平均粗糙度和均方根粗糙度)进行预测,同时模拟加工中刀具引导角和倾斜角对加工表面质量的影响。最后通过在不同切削条件下进行五轴球头铣削试验,验证了所提出的表面形貌预测模型的有效性。     

模具高速切削数据库的研究与开发

采用结构化程序和规范化数据库技术开发了模具高速切削数据库系统，使用该系统可实现模具材料查询、刀具选择和切削用量查询。针对高速切削数据缺乏的问题，本系统采用了基于实例推理技术，实现为新工件材料、新刀具材料提供合理加工工艺和加工参数。     

细长轴车削与磨削参数优化研究

针对细长轴车削和磨削加工参数的选择问题,建立以工件刚度、刀片强度、刀杆刚度、机床进给机构强度、机床功率、机床参数、加工表面粗糙度、加工余量等作为约束条件,以切削速度、进给量、背吃刀量、工件转速、磨削余量、径向进给量等参数为优化变量,以车、磨多工序成本最低为目标的切削参数优化模型。以某型号电机轴为案例,运用MATLAB模式搜索工具箱对其车削和磨削参数进行寻优,与切削参数的传统选择方法比较表明,工序成本可降低35%以上,从而验证了优化模型的有效性。     

Tool wear control in single-crystal diamond cutting of steel by using the ultra-intermittent cutting method

Excessive tool wear is a major drawback to the ultraprecision cutting of steel with geometrically defined single-crystal diamond tools. This paper presents a new approach to reduce this wear. In general, the wear of the diamond tool is due to chemical reactions such as diffusion into the steel, oxidation, graphitization, and carbide formation under cutting conditions of high temperature and high pressure. To suppress these types of chemical reactions, the contact time between the diamond tool and the steel in the cutting process was controlled by intermittent cutting method such as fly-cutting or milling. A series of intermittent cutting experiments were carried out to control the tool–workpiece contact time in one cutting cycle by changing the cutting speed and cutting length in each cutting cycle. The experimental results showed that the diamond tool wear was highly dependent on the tool–workpiece contact time, regardless of the cutting speed, and that the wear was greatly reduced by decreasing the contact time to less than 0.3 ms under these cutting conditions. It is expected that steel can be successfully cut with a single-crystal diamond tool by controlling the tool–workpiece contact time.     

A novel approach for real-time prediction and prevention of tool chipping in intermittent turning machining

An integrated tool condition monitoring system, based on a novel signal processing approach, for online prediction and prevention of tool chipping in intermittent turning is presented. It identifies the unstable crack propagation features of the prefailure phase, independent of the cutting parameters and workpiece material. A correlation between the chipping size and these features was developed for decision making, to protect machined surfaces. Experimental validation results confirmed the accuracy of the proposed system. The time required for signal processing, decision making and communication with the machine controller allows stopping the operation before part damage. No such system is presently available.     

基于夹丝热电偶法的高速切削温度测量

切削温度与刀具磨损、工件加工表面质量及加工精度密切相关，用红外辐射、超热辐射等非接触式的测温方法只可以实现局部切削温度的间接测量。文章设计一种利用夹丝热电偶实现高速切削过程瞬时切削温度测量的直接接触式计算机辅助测温系统，该系统利用PCI-1200卡采集热电偶测温装置传输的数据，通过Labview软件分析处理，具有显示温度波形曲线、标定热电偶曲线能力。最后通过高速切削淬硬钢试验测量了刀具／工件界面的瞬时温度，定性分析了切削速度、刀具磨损、加工参数对切削温度影响的变化规律。     

准双曲面齿轮数控加工仿真系统设计

根据准双曲面齿轮数控加工原理,提出了CNC铣齿机、齿轮毛坯和盘铣刀实体模型的具体构建方法;利用简化的齿轮毛坯实体模型和盘铣刀实体模型做布尔减运算,在计算机上实现了模拟工件材料的去除过程;通过加工仿真结果和实际加工结果对比,验证了加工仿真方法的正确性.所获得的仿真结果可为齿面接触分析和有限元应力分析提供精确的实体模型.     

Statistical analysis of the effects of machining parameters and workpiece hardness on the surface finish of machined medium carbon steel

The objective of this study is to ascertain the effect of machining parameters and workpiece hardness on surface roughness of machined components and to develop a better understanding of the effect of process parameters on the machined surface. Such an understanding can provide insight into the problems of controlling the finish of machined surfaces when the process parameters are adjusted to obtain a certain surface finish. The collected data were analyzed using parametric analyses of variance (ANOVA) with surface finish as the dependent variable and hardness of the workpiece material, cutting tool position from the surface of the clamping device (chuck), depth of cut, cutting velocity, and cutting feed as independent variables. The results showed that surface roughness is significantly affected by the workpiece hardness, cutting feed, cutting speed, depth of cut, cutting tool position from the chuck, and their interactions with each other. The results suggest that feed rate and cutting speed can be adjusted to produce a certain surface finish when the position of the cutting tool from the surface of a clamping device or the hardness of the workpiece is changed.     

Creation of Flat-End V-Shaped Microgrooves by Non-Rotational Cutting Tools

The study deals with the creation of V-shaped microgrooves with flat-end, which play an important role in case of generating intermittent grooves. Microgrooves by use of rotational cutting tool have a long radius in disengagement from the workpiece. Thus, two cutting methods by use of non-rotational cutting tool are devised so that V-shaped microgrooves with flat-end can be created. The first method makes use of straight chips generated under some cutting condition. Non-rotational cutting tool compresses the chips at the groove end and cuts the excessive parts of chips over the plane. The second method is to transcribe the surface of a tool indented vertically into a workpiece. As a result, it is experimentally found that the methods enable the creation of flat-end microgrooves.     

An automated monitoring solution for avoiding an increased number of surface anomalies during milling of aerospace alloys

The demand for automated machining systems to enable the increase of process productivity and quality in milling of aerospace safety critical components requires advanced on-line monitoring and supervision systems to identify and reduce the number of workpiece surface anomalies caused by faulty tooling. It is well known that chipping or breakage of only one tooth of a milling cutter can lead to extensive damage to the machined surface. Therefore, implementing a process monitoring solution that can detect workpiece surface anomalies associated with the cutting tooth that generated them could be beneficial for proposing more efficient process supervision systems. The system presented in this paper is directed towards real-time control of the contact length of each tooth of a milling cutter with the scope of reducing the amount of workpiece surface anomalies. The proposed control solution consists of: (i) an automated process monitoring part, that, through signal analysis, automatically improves the reliability of fault detection; (ii) a signal based decision and supervision system for the avoidance of surface anomalies or tool malfunctions. The novelty of this supervision system comes from the fact that it is automatically acquiring Acoustic Emission (AE) and cutting forces, adjusts the monitoring parameters accordingly and transmits decision commands to the machine. The supervision system makes use of the sensor fusion and an original methodology for the detection of process malfunctions, to control the movement of the tool. This is directed towards the adjustment of the individual feed per tooth for each cutting edge, and if necessary reduce it to zero for a cutting tooth that is creating the surface damage. The efficiency of the proposed process supervision system is proven to avoid the generation of surface anomalies in milling of a Ni-based alloy used for the manufacture of parts for gas turbine engines.