热轧轧辊辊面磨削缺陷

本钢热连轧厂轧辊车间主要承担3条热连轧生产线的备辊准备工作,每月磨削各品种的轧辊6300支以上。文章列举了轧辊磨削过程中常常存在辊面磨削缺陷,常见有:振纹、斜振纹、走刀痕、斑块、磨削烧伤及磨削划伤缺陷等几种。针对各种磨削缺陷特性,逐一进行了原因分析和改善性的改进工作。通过采用轧辊材质与各种砂轮材质的合理匹配、优化轧辊磨削工艺等改善性措施,最终消除轧辊表面的磨削缺陷。同时,有目的性地制定了轧辊磨削质量标准和图谱,使取得的成果固化,有效地提升轧辊磨削质量,向产线提供了高品质的轧辊,为热轧厂轧出精品板材产品提供了坚实的保障。     

粗轧铜带"振纹"的分析

粗轧铜带时 ,在带材表面上产生振纹。作者对振纹现象进行了测试、试验并对振纹现象进行了分析 ,找出了解决问题的方法     

陶瓷CBN砂轮在船舶曲轴磨削中的应用

对陶瓷结合剂CBN砂轮工作层配方和砂轮基体进行优化设计后,制备了磨船舶用曲轴用CBN砂轮,并进行了磨削试验研究,对磨削后的工件表面粗糙度和振纹进行了分析。实验结果表明:砂轮修整方法对砂轮的应用效果影响较为显著;砂轮修整的最佳工艺参数为:滚轮转速3000r/min,砂轮转速450r/min,纵向移动速度250mm/min,可得到的工件表面粗糙度值Ra≤0.32μm,且无振纹、烧伤。     

陶瓷CBN砂轮修整方法及修整工艺研究

本文论述了陶瓷CBN砂轮修整的重要性,对修整的整形和修锐两个步骤进行了评述.使用电镀金刚石滚轮对用于数控磨削凸轮轴的高速陶瓷CBN砂轮进行了修整工艺的实验研究,得出了滚轮与砂轮的速差是影响修整效果的重要因素,顺修的修整效果优于逆修方式.顺修时速差不能过小,否则容易造成磨削振纹.必须使用逆修的场合,速差不能过大,建议对砂轮采取降速修整.根据实验结果,得出了速差的合适范围--顺向修整速差不能小于11 m/s,逆向修整速差不能大于95 m/s;滚轮相对砂轮纵向走刀速度推荐使用600 mm/min.在此参数范围内修整出的砂轮,用于磨削冷激铸铁凸轮轴凸轮,表面粗糙度为0.63μm,凸轮桃尖部无振纹、麦穗纹及单斜纹,质量达到了工件的技术要求.     

外圆磨削工件表面螺旋纹的控制

阐述了外圆磨削中影响表面质量、粗糙度、尺寸精度的主要因素和磨削中螺旋纹的控制方法.在实践中应用该方法可以大大改善工件加工质量,解决了外圆磨削中较棘手的技术问题.     

超声波振动修整砂轮寿命的试验研究

本文就超声波振动修整砂轮能否提高寿命的问题进行了试验研究。文中详述了在外圆磨床上的试验装置及先进的振纹监测方法。列举出外圆切入磨削和内孔磨削时砂轮寿命的对比试验结果。最后归纳了平面磨削、外圆磨削和内孔磨削的试验情况,证明超声波振动修整确实能提高砂轮的寿命,但它是有条件的。在某些磨削类型和条件下能提高,在某些情况下不能提高。生产中欲采用这种新工艺时,必须进行科学试验,掌握其规律性。     

铝热轧带材表面振纹产生的原因与改善措施

1+3铝热连轧机生产的带材表面出现振纹,影响产品质量。根据振纹的特征并结合轧机的振动机理,确定振纹是由轧机的垂振现象引起的。分析了影响垂振的设备、工艺润滑、控制系统等因素,发现当卷取速度为1.1 m/s～1.4 m/s时,力的相互耦合触发轧机自激振动。通过优化带材中间坯轧制速度、轧制温度、乳液喷射压力、喷射流量及喷射模式,控制带材卷取速度,避开1.1 m/s～1.4 m/s卷取速度区间,消除了带材表面振纹。     

外圆高速磨削颤振可靠性研究

磨削颤振严重影响了加工精度和表面质量，以外圆高速磨削为研究对象，基于再生颤振机理，建立了工件-砂轮动力学模型，求解了理论临界磨削深度，并绘制了稳定性叶瓣图；考虑动力学参数的不确定性，建立了磨削加工系统可靠性模型，采用改进一次二阶矩法求解磨削深度的可靠性；通过模态试验获得系统频响函数，并计算了磨削颤振可靠度；最后，选取15种工况开展颤振可靠性磨削试验，并通过工件表面振纹对颤振进行辨识。结果表明稳定性叶瓣图预测结果可能存在误差，利用磨削颤振可靠度对其评判，可提高预测结果的准确性。     

超高速磨削主轴系统的动态有限元分析

运用有限元分析软件ANSYS建立超高速磨床主轴系统的三维有限元模型,并对其进行模态分析,得到各阶固有频率和振型。针对超高速磨削过程中由转速产生的离心力的影响,先对主轴系统进行了静力分析,然后对其进行模态分析,获得各阶固有频率和振型。通过比较得知:考虑预紧力后,主轴系统固有频率都有提高。通过公式计算获得各阶固有频率所对应的临界转速,为磨削加工时避开共振频率提供理论指导。考虑到磨削力对主轴系统的激振力作用,利用Full法对主轴系统进行谐响应分析,获得了主轴跨中节点随激振力频率变化的幅频响应曲线,识别了产生共振的激振力频率。提出了进一步提高主轴动态特性的工艺措施。     

振动影响刃口磨削质量的分析

为了保持刃口磨削过程的稳定性，寻求刃口磨削振动的产生和发展规律，从而避免和抑制磨削振动；砂轮和砂轮轴的偏心是磨削过程中的主要振动源，通过对偏心而产生的附加动力的分析，列出振动方程，解出通解及振副表达式，对提高工件的加工质量和生产率具有重要意义。     

基于非线性磨削模型的稳态与颤振抑制的研究

在轧辊磨削过程中,选择稳态叶图边界曲线附近的参数易发生颤振,使得轧辊磨削工艺参数选择过于保守,导致磨削效率严重降低的问题。为此,通过引入Duffing振子,构建三自由度非线性轧辊磨削动力学模型。采用数值计算的方法,研究过程参数在稳态边界附近变化对轧辊磨削颤振的影响;为抑制轧辊磨削颤振,提出混沌摄动方法抑制颤振。结果表明：所提方法有良好的颤振抑制效果,为实际加工过程中参数选择和轧辊磨削颤振抑制提供参考。     

新型陶瓷托辊专用磨床磨削颤振稳定性分析

为了避免陶瓷托辊专用磨床在加工过程中产生颤振而降低磨削质量,根据陶瓷托辊磨削加工机制,建立了陶瓷托辊磨削加工过程数学模型,通过MATLAB计算分析得出磨削深度与主轴转速的稳定性叶瓣图,确定了陶瓷托辊磨床在磨削深度低于4 mm时可无颤振稳定磨削。研究结果为陶瓷托辊专用磨床稳定磨削加工提供了参考。     

一种新型磨胶辊砂轮制造技术

在专利ZL201510030023.1《一种新型磨胶辊砂轮及其制备方法》的基础上,对新型磨胶辊砂轮中的气孔作用机理进行理论探讨。新型磨胶辊砂轮与传统的磨胶辊砂轮相比,不易发生气孔堵塞问题,具有良好的工件加工能力,在磨削工件时不会产生振纹和划伤痕迹,有利于提升工件的加工品质、提高劳动效率。通过试验样品磨削应用反馈:该新型磨胶辊砂轮气孔率达到70%~80%,比一般大气孔碳化硅砂轮高16%以上;回转破裂速度达到120 m/s,比一般大气孔碳化硅砂轮强度提高20%以上;磨削后工件表面光洁度有所提高,修复周期延长2个月以上。并且,通过针对性地选择刚玉空心球粒度,能够制造出具有设计的性能的砂轮,能有效地避免传统磨胶辊多孔磨具的一些问题,比如大气孔碳化硅砂轮常见的烧成黑心、使用强度偏低、成孔剂不环保等问题,同时该新型磨胶辊砂轮的生产工艺性能稳定可靠,易于推广应用。      

The measurement of forces in grinding in the presence of vibration

Most investigations of chatter have made the assumption that torsional vibration is not a significant factor. Some recent work has shown that chatter in grinding is affected by a change in the torsional stiffness of the workpiece drive. Also, a theoretical model of grinding chatter has been developed that confirmed the significance of torsional effects. However, the model for the grinding force was assumed to be a dynamic equivalent of a published steady-state model. This paper describes tests conducted to measure the variation in force caused by an oscillation in workpiece speed. The oscillating test results indicate that the torsional vibration of the workpiece may well be a significant effect on chatter in grinding. Moreover, as the grinding force changes with workpiece speed, it may be possible to use variation of workpiece speed at high frequency to reduce chatter.     

基于空化效应的功率超声珩磨再生型颤振研究

功率超声珩磨加工过程中的颤振影响因素很多,不仅包含物理磨削过程和机械振动环节,还包含了高频振动和超声波传动系统,是一个非常复杂的复合振动系统。通过建立珩磨颤振动力学模型,重点研究珩磨中空化泡溃灭产生辐射声压对再生型颤振的影响,结果表明:决定功率超声珩磨再生型颤振的主要原因为磨削厚度;空化泡溃灭产生的辐射声压会加剧系统颤振的频率,但对系统颤振的时域图变化趋势和振幅的大小基本没有影响。     

Effectiveness of continuous workpiece speed variation (CWSV) for chatter avoidance in throughfeed centerless grinding

The continuous rotation speed variation is demonstrated to be an efficient method to avoid regenerative chatter in different machining processes. This paper presents a time-domain dynamic model for throughfeed centerless grinding process that can predict chatter by means of part roundness error evolution. Continuous workpiece speed variation (CWSV) has been implemented in this model to analyze the influence of this disturbing method on the dynamic instability. Experimental results have validated the model and verified the effectiveness of CWSV for chatter avoidance and surface finish and dimensional tolerances improvement. It has been demonstrated that the selection of the optimal variation parameters is an important factor not only for chatter avoidance, but also for the stability of surface finish and dimensional tolerances since workpiece speed variation has a direct influence on throughfeed rate and grinding forces.     

A study on chatter boundaries of cylindrical plunge grinding with process condition-dependent dynamics

This paper presents a systematic study on the chatter characteristics of cylindrical plunge grinding processes. Chatter occurrence under a wide range of operating conditions is experimentally identified. The unique transient chatter behaviors during spark-in and spark-out of plunge grinding are also studied; and the transient chatter occurrence is separated from the steady-state chatter occurrence, which is used to define the chatter boundaries.It is shown that the measured structure dynamics of the wheel/workpiece exhibit strong dependency on grinding conditions. The dynamic/chatter model of cylindrical plunge grinding [H. Li, Y.C. Shin, A time-domain dynamic model for chatter prediction of cylindrical plunge grinding processes, ASME Journal of Manufacturing Science and Engineering 128(2) (2006) 404–415] is improved to handle the grinding force-dependent structure dynamics, and the modified model is validated by comparing the predicted chatter boundaries with experimental chatter conditions.     

An investigation of in-process measurement of ground surfaces in the presence of vibration

Recent work on chatter in grinding has shown that the presence of torsional vibration is potentially significant. Controlling the torsional characteristics of the workpiece drive may eliminate chatter. These findings lead to a re-examination of the fundamental grinding force equation, where the surface speeds are conventionally assumed to be constant. If torsional vibration is present for both the grinding wheel and the workpiece, there will be two extra terms in the grinding force equation. Traditionally, experimental measurements used to try and verify the cutting force model have been undertaken under non-vibrating conditions. Any attempt to verify a cutting force model under vibrating conditions requires the continuous measurement of several parameters as a function of time. One of these is the instantaneous depth of cut, δ. This paper presents experimental results for an investigation into the in-process measurement of δ under chatter conditions on a cylindrical grinding machine. This initial investigation has indicated that such a measurement is very difficult and is prone to errors if chatter is present. It is proposed and anticipated that controlled (vibration) excitation under inherently stable conditions will allow for the required measurements to be made with sufficient accuracy.     

An active system of reduction of vibrations in a centerless grinding machine using piezoelectric actuators

Centerless grinding has been extensively used in production engineering to produce accurate cylindrical parts together with high productivities. On the other hand, regenerative chatter vibrations are one of the major problems that limit the ability to produce round workpieces. This constraint can be solved selecting proper machine setup conditions, which still largely relies on a trial and error method, and sometimes this approach is not optimum in a productivity sense. This paper shows a novel method to reduce chatter vibrations in a centerless grinding machine using actively controlled piezoelectric actuators. A simplified model of the machine is used to simulate the behavior of several commercially available piezoelectric actuators in two different locations of the machine. Based on these simulations, a selection of proper actuators and their optimal location is obtained and the control system is implemented experimentally. Experimental results show that the control strategy provides a stabilizing effect on chatter. Thus, the viability of using piezoelectric actuators as active components is demonstrated, providing an important advance in the knowledge of chatter control in centerless grinding machines.     

Analysis of chatter in contour grinding of optical materials

Chatter that limits ground surface finish has been observed in the deterministic microgrinding of brittle optical materials. In this article, the classical single degree of freedom model for chatter, accounting for both work and tool regenerative effects, is adapted for contour grinding optical surfaces. A linearized expression for the cutting stiffness is developed for the contour grinding geometry based on Preston’s law. Techniques developed to measure the machine frequency response function (FRF) and the Preston coefficient, needed as inputs to the simulations, are described. Numerical simulations based on this model are used to predict the grinding system behavior and to investigate process parameters affecting chatter stability. The stability limits observed during grinding experiments on optical glasses are in good agreement with the simulation results.