无心磨削成圆过程仿真系统的研究与开发

首先介绍了工件成圆误差的定义及计算方法,然后在分析无心磨削加工的工件成圆过程的基础上,以VC、OpenGL为开发工具,采用VC与MATLAB联合编程的方法,设计开发了无心磨削成圆过程仿真系统.仿真结果与实验数据一致,具有良好的实用价值.     

无心磨削成圆过程仿真系统的研究与开发

首先介绍了工件成圆误差的定义及计算方法,然后在分析无心磨削加工的工件成圆过程的基础上,以VC、OpenGL为开发工具,采用VC与MATLAB联合编程的方法,设计开发了无心磨削成圆过程仿真系统。仿真结果与实验数据一致,具有良好的实用价值。     

无心磨削动态成圆模型与数值仿真

为了对无心磨削系统的工件动态成圆过程进行真实有效的数值仿真以及对工件的最终圆度进行科学合理的预测,建立了一种考虑工件中心瞬时位置变化的无心磨削动态成圆模型并对其进行了数值仿真。首先分析了磨削过程中由于工件表面形貌改变导致的工件定位中心位移以及磨削系统的振动引起的工件中心位移对工件中心瞬时位置变化的影响,然后综合考虑无心磨削过程中砂轮和工件之间的相互耦合作用、材料去除关系建立了工件磨削动态成圆模型,最后利用所建立的动态成圆模型和模拟工件材料去除及圆度变化的迭代算法,对工件外圆动态成圆的过程进行了数值仿真,再现了工件材料去除和轮廓形成的整个过程。通过对仿真算例结果的分析,证实了所提出的无心磨削动态成圆模型和迭代算法的真实性和合理性,对无心磨削成圆过程研究具有一定指导意义。     

无心磨削工件质量的在线控制方法

无心磨削工件质量在很大程度上取决于工艺本身。在无心磨削过程中零件的中心线是漂移的。工件上的不规则部分与刀板或导轮接触时会产生这种现象，从而导致工件的圆度误差。文章阐述无心磨削工艺的计算机模拟试验工作，它表明有可能通过导轮的运动来提高被磨工件的圆度。所列程序提供了可保证无心磨削质量的新方法。     

曲轴非圆磨削运动中动态误差及补偿

动态误差是影响曲轴非圆磨削加工精度的主要因素,动态误差补偿可实时修正磨削过程的各种误差,保证补加工工件的加工精度.通过分析曲轴非圆磨削过程中动态误差产生的原因,对非圆磨削中数控系统的伺服滞后误差进行了定量分析,并对以恒线速度为基础的运动模型进行了仿真计算,计算结果表明,伺服滞后误差严重影响加工精度,且数控系统的调整只能减少伺服滞后误差,不能消除伺服滞后误差.提出了采用神经网络预测曲轴非圆磨削过程的误差,并对补偿数据进行必要的延迟处理后进行相应的补偿,以解决在线测量的角度偏差.通过离线测量加工试验表明,采用径向基函数网络较好地解决了曲轴非圆磨削过程中的误差补偿.     

凸轮非圆磨削动态误差预测及补偿

对凸轮非圆磨削过程中伺服跟踪误差产生的原因进行分析,并定量计算了凸轮非圆磨削中数控系统的伺服滞后误差,并指出了数控系统的调整只能减小伺服滞后误差,不能消除伺服滞后误差.根据工件的实际测量结果,采用神经网络预测凸轮非圆磨削过程的误差,并进行相应的补偿.通过实际磨削测量结果表明,采用RBF网络能较好地解决凸轮非圆磨削过程中的误差补偿.     

无心磨削过程中的谐波振动模式

尽管对工件的无心磨削成圆机理已有一定的研究,但关于工件圆度误差的振幅频谱,究竟在无心磨削过程中怎样产生,至今没有详细叙述。本文中,与工件圆度误差的频谱分析对应,建立了磨削过程中的工件谐波分量的振动模式。在此基础上,以振动方程中的放大系数,解释了为什么在无心磨削过程中,2次椭圆及3次棱圆的振幅较大;接着,分析了谐波振动模式的瞬时不稳定特性;最后,给出了振幅频谱图中振幅局部最大值的谐波次数分布原则,并从接触刚性的角度,介绍了改善表面有缺口工件的圆度误差的磨削实例。     

最佳无心磨削条件的设定

一、前言无心磨削因其工件支承刚性较高，是一种兼备高效、精密双重优点的加工方法。但是，磨削工件的圆度误差又不可避免地受到中心高角r，托板项角中，工件转速n。及单位磨除率Z’等诸多因素的制约。为将无心磨削的圆度误差控制在最小值，本研究通过计算机模拟分析，探讨了最佳无心磨削条件（几何关系和工艺参数）的设定，并通过磨削试验对其进行验证。实践结果表明：1．通过计算机模拟来设定最佳无心磨削条件是一种行之有效的方法；2．调整工件转速n。可减小磨削工件的圆度误差；3．无心磨削条件中的关键参数是中心高角r和加工弹性参数K…     

基于OpenGL无心外圆磨削仿真系统的研究

无心磨削是一种精密、高效的加工方法,在机械制造领域占有重要地位,以切入式外圆无心磨削为研究对象,介绍了仿真系统中各功能模块,对系统开发过程中所使用到的技术要点进行探讨,并对3DS模型在仿真系统中的读取与重现进行了分析,采用OpenGL技术实现了无心外圆磨削加工过程的仿真系统,提出了根据工件中心高的理论优化值计算托板高度的方法,在时域中对工件真圆度和磨削力进行了仿真,为进一步研究无心磨削的动态特性和提高磨削加工精度提供了依据。     

曲轴非圆磨削中基于差分进化算法的变参数交叉耦合轮廓控制

曲轴非圆磨削通常采用补偿单轴伺服跟踪误差的方法来提高连杆颈轮廓加工精度,但磨削运动中大惯量砂轮架会严重影响伺服系统的高速响应性,导致单轴伺服跟踪误差补偿轮廓误差效果不理想.因此引入双轴联动交叉耦合控制思想,首先工件旋转轴与砂轮架直线轴的联动运动被近似为两根直线轴联动,并建立曲轴非圆磨削轮廓误差模型,在此模型基础上设计交叉耦合控制系统.为了弥补这种近似对非线性轨迹控制带来的不足,研究分段变参数的交叉耦合控制策略,并以工件轮廓误差最小为目标,采用差分进化(Differential evolution,DE)算法逐段对控制器参数进行优化.仿真实例结合试验表明:在基于DE算法优化的变参数交叉耦合控制下,曲轴非圆磨削理论轮廓精度较普通比例微分和积分控制或交叉耦合控制有所提高.     

Modeling of the axial movement of parts during centerless through-feed grinding

There are two major differences between the centerless infeed grinding process and the centerless through-feed grinding process. One is an axial movement of workpieces, and the other is that several workpieces are ground simultaneously and continuously by through-feeding. Because of these dilfferences, through-feed ground parts inherently possess not only the roundness error but also the tapering error. The aims of the research reported in this paper are to examine this inherent tapering characteristic and to find the effects of grinding variables (center height angle, regulating wheel tilt angle, and shape of grinding wheel surface). To accomplish the objectives, experiments were carried out using two types of cylindrical workpiece shapes. Also, computer simulations were performed using the 3-D through-feed grinding model.     

COMPUTER SIMULATION OF BELOW-CENTER AND ABOVE-CENTER CENTERLESS GRINDING

Centerless grinding of ceramic components in the conventional above-center mode under aggressive conditions often results in workpiece spinning. One way to avoid workpiece spinning is to use below-center grinding, but this can lead to problems with part rounding and lobing. The present investigation was undertaken to develop a practical simulation to assist in the selection of acceptable set-up conditions for centerless grinding. From the initial workpiece profile and set-up conditions as input, the simulation predicts workpiece spinning and the progressive change in the workpiece profile for both above-center and below-center grinding. Simulation results for workpiece lobing were found to be consistent with experimental results obtained for below-center grinding of zirconia specimens.     

Modeling of the centerless through-feed grinding process

A computer simulation method for investigating the form generation mechanism in the centerless through-feed grinding process is described. The length of the contact line and the magnitude of the grinding force between the grinding wheel and workpieces, vary with the change in the axial location of the current workpiece during grinding. Thus, a new coordinate system and a grinding force curve of previous and/or following workpieces are introduced to treat the axial motion. Experiments and computer simulations were carried out using four types of cylindrical workpiece shapes. To validate this model, simulation results are compared with the experimental results.     

叶片机器人砂带磨抛点云匹配算法优化

为解决机器人磨抛路径中工件坐标系难以计算的问题及校正工件装夹误差,将三维点云配准技术应用到叶片机器人砂带磨抛系统中。由三维激光扫描仪扫描工件型面获得工件点云,采用基于主成分分析(PCA)的全局配准算法和改进的迭代最近点(ICP)算法完成了扫描点云和工件模型离散点云间以及不同工件扫描点云间的匹配,以获取工件坐标系和校正工件装夹误差。相关仿真和试验结果表明,优化后的算法在匹配速度与精度上有了长足改进,且加工后产品精度和质量都能满足实际加工要求。     

A feasibility study of microscale fabrication by ultrasonic-shoe centerless grinding

The present authors proposed a new centerless grinding technique, namely ultrasonic-shoe centerless grinding, which they validated experimentally in a previous study [Wu Y, Fan Y, Kato M, Wang J, Syoji K, Kuriyagawa T. A new centerless grinding technique without employing a regulating wheel. Key Eng Mater 2003;238–239:355–60]. Rather than a regulating wheel as in conventional centerless grinding, the new method uses a plate-shaped ultrasonic shoe, on the end face of which micro elliptic motion is generated, to support the workpiece and control its rotational motion. This enables the fabrication of a microscale cylindrical component less than 100 μm in diameter with an extremely large aspect ratio, which is extremely difficult to produce by conventional machining techniques. In the present study, in order to develop a novel technique for the fabrication of microscale cylindrical components, first an apparatus capable of microscale fabrication was designed and constructed based on the ultrasonic-shoe centerless grinding method. Following initial performance tests, the apparatus was tested by conducting a grinding run on a tungsten carbide test-piece, 0.6 mm in diameter and 15 mm in length. The result was a microscale cylindrical component, around 60 μm in diameter and 15 mm in length, with an aspect ratio of over 250, which validated the new technique proposed for microscale fabrication.     

Modeling of the centerless infeed (plunge) grinding process

A computer simulation method for investigating the form generation mechanism in the centerless infeed (plunge) grinding process is described. For a 3-D simulation model of form generation, contact points are assumed to be on least squares contact lines at the grinding wheel, regulating wheel, and work-rest blade. Using force and deflection analyses, the validity of this assumption is shown. Based on the 2-D simulation model developed in the previous work and the least squares contact line assumption, a 3-D model is presented. To validate this model, simulation results were compared with the experimental works. The experiments and computer simulations were carried out using three types of cylindrical workpiece shapes with varying flat length. The experimental results agree well with the simulation. It can be seen that the effect of flat end propagated to the opposite end through workpiece reorientation.     

Selections of working conditions for creep feed grinding. Part(III): avoidance of the workpiece burning by using improved BP neural network

In this study, the grinding force of the creep feed grinding are modeled and forecasted by using the improved back propagation neural (BPN) network. The results show that the grinding energy can be accurately predicted by the application of the grinding force model. Due to the previous paper, the workpiece burning occurs as the grinding energy is greater than the critical grinding. Thus, a judgment for the occurrence of the workpiece burning can be achieved. Comparing with the experimental results, the applied algorithm of the improved BPN network is proved to be effective in forecasting the working conditions of the workpiece burning. Thus, a selection scheme of working conditions in view of the avoidance of the workpiece burning is further developed. Considering the working efficiency, the working conditions are selected to maximum metal removed rate, MRR_max. The results show that a larger size of wheel is available to have a better working efficiency.     

Automatic compensation for grinding wheel wear by pressure based in-process measurement in wet grinding

This paper deals with an application to automatic compensation of grinding wheel wear by a pressure based in-process measurement method in wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap by the rotation, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. No electromagnetic properties of the workpiece and grinding wheel affect measured results. This method is applied to a CNC surface grinding machine. The pressure distribution and the relationship between the pressure and the gap length are measured. The pressure is decreased with the increase of the gap length. Its dispersion is around 1% for 0.5 μm-wear of a grinding wheel with 250 μm grit size. The dimensional error of a workpiece using the feedback of the wear is less than the feeding step, for the compensation, of 1 μm.