非轴对称非球面平行磨削误差补偿技术研究

针对非轴对称非球面的成形加工法柔性不足及球形砂轮加工法对工具和机械的要求太高的缺点,提出采用普通圆弧金刚石砂轮加工的平行磨削法。对于新方法加工中存在的加工误差问题,提出在非轴对称非球面加工中使用带倾角圆弧修整器及对主轴半径和副轴半径误差采用离线补偿的加工技术。通过理论分析和试验表明此方法可达到提高非轴对称非球面的加工精度的效果。     

砂轮几何参数对非球面轨迹包络磨削的影响研究

针对非球面轨迹包络磨削过程中砂轮磨损而影响加工质量的问题,根据非球面轨迹包络磨削成形原理,分析了轴对称非球面、非轴对称非球面加工中盘形砂轮的几何参数对轨迹包络磨削加工过程的影响。分析结果表明:盘形砂轮圆弧截面的圆弧直径、砂轮宽度、砂轮直径等几何参数将直接影响到参与磨削的砂轮磨粒的数量。合理选择盘形砂轮的几何参数,可以有效地增加参与磨削的砂轮磨粒数量,从而减少盘形砂轮的磨损,这对于提高非球面轨迹包络磨削加工精度有着非常重要的意义。     

用单片机控制砂轮修整器

我们利用单片机设计了新型砂轮修整器,用于磨削滚珠螺母内螺纹滚道的砂轮修整,提高了加工精度。用单片机控制的双圆弧砂轮修整器工作原理见图1。     

金刚石滚轮成形砂轮修整器的结构设计

针对加工轴类工件时,常会遇到尺寸精度要求高、表面粗糙度值小的各种圆弧的难加工问题,提出采用成形磨削法进行圆弧的加工,并针对圆弧加工用的成形砂轮,设计出金刚石滚轮成形砂轮修整器。     

成型磨削砂轮修整中的数控加工预处理方法

成型砂轮数控修整器要求具有两移动轴加一转动轴的三轴联动功能，需要设计相应的数控加工预处理程序。本文首先解决了成型砂轮曲线的光顺处理问题，针对圆弧加工过程中必须保证修整工具始终处于砂轮曲面法向的要求，提出了细分圆弧的可行性解决方法。     

多功能砂轮修整器的设计与应用

1　引言在精密零件的磨削加工中 ,圆弧形面的磨削尤其是轴承外环内滚道和内环外滚道的磨削是一个技术难点 ,而砂轮的修整对磨削精度起着重要作用。传统的砂轮修整是通过砂轮修整笔进行手工修整 ,或者采用成型修整器 (如滚轮 )进行修整。但这两种方法修整后的砂轮都会产生圆弧形状误差 ,影响加工后工件的形状精度。影响砂轮修整精度的原因有两方面 :一是修整器本身的精度 ;二是操作不当。如在使用砂轮修整笔手工修整砂轮时 ,若工人操作不当 ,使修整器与过砂轮中心线的水平面偏离 ,则在修整笔尖Ａ处 ,修整笔的运动轨迹在水平面内为圆弧曲线 2 …     

金刚石滚轮成形砂轮修整器的结构设计

加工轴类工件时,经常会遇到尺寸精度要求高、表面粗糙度值小的各种圆弧的难加工问题,为了解决这一问题,本文提出采用成形磨削法进行圆弧的加工,并针对圆弧加工用的成形砂轮,设计出金刚石滚轮成形砂轮修整器。     

树脂基圆弧金刚石砂轮的在位精密成形修整技术

针对球面、非球面及自由曲面超精密磨削加工用树脂基圆弧形金刚石砂轮难以精密修整的问题,提出基于旋转绿碳化硅(GC)磨棒的在位精密成形修整技术。在分析GC磨棒和圆弧砂轮几何关系的基础上,确定修整过程中圆弧插补轨迹的补偿方法及GC磨棒运动轨迹的设计方案。采用KEYENCE激光测微仪采集砂轮圆弧特征点,表征圆弧砂轮的修整状况。研究不同粒度的GC磨棒、进给深度和圆弧插补速度对圆弧金刚石砂轮修整率和修整精度的影响规律。研究结果表明,该修整方法可根据加工曲率半径要求实现不同圆弧半径砂轮的精密在位修整,修整后可自动消除砂轮垂直方向的位置偏差;采用400#和800#的GC磨棒对D3和D7砂轮均有较高的修整率(0.7~6.7);与400#和1500#的GC磨棒相比,800#GC磨棒更适合粒度为D3和D7圆弧金刚石砂轮的精密修整;相比圆弧插补速度,进给深度对砂轮的圆弧半径尺寸误差和形状误差影响更大,进给深度越小,圆弧半径尺寸误差和形状误差越小;修整后两种砂轮的圆弧半径误差均可控制在5%以内,D3砂轮的形状误差可控制在3μm/4 mm以内,D7金刚石砂轮可控制在6μm/4 mm以内,修整后比修整前形状误差提高14倍左右。     

砂轮圆弧数控修整研究

介绍了传统手工方法修整砂轮的不足,阐述了数控砂轮修整器圆弧修整原理,通过合理选择砂轮修整参数和修形方式可提高砂轮表面修整质量,达到砂轮端面直角边圆弧修整的目的。     

车削套圈沟道曲率样板的设计

随着沟道磨削方式的改变，根据摆动磨削沟道工艺设计沟道曲率样板的公式不适用切入磨削。切入磨削的特点是：用圆弧砂轮修整器把砂轮的外缘修整成所需要的圆弧半径，然后用已成形的砂轮切入套圈沟道，即可磨出所需要的圆弧沟道，所以砂轮的几何形状决定了套圈的加工质量。     

圆弧金刚石砂轮三维几何形貌的在位检测和误差评价

针对非球面光学元件加工对圆弧金刚石砂轮形状误差测量的需求,提出了砂轮三维几何形貌在位检测与误差评价方法。建立了砂轮外圆面螺旋扫描轨迹测量数学模型,利用位移传感器获取了砂轮表面轮廓数据;对得到的数据匀滑滤波后沿圆周展开并进行插值处理,得到砂轮三维几何形貌。然后,根据非球面平行磨削加工特点,提出评价圆弧砂轮形状精度的指标。通过提取三维几何形貌轴截面轮廓,进行最小二乘圆弧拟合得到不同相位处的圆弧半径与圆心坐标,并由误差分离获得砂轮表面圆弧的圆度误差、圆周跳动误差及轮廓圆心轴向偏差。最后,对非球面加工圆弧金刚石砂轮进行检测,获得了砂轮的三维几何形貌以及多个关键尺寸及其误差数据:即圆弧金刚石砂轮的平均圆弧半径为55.442 3mm,半径波动极差为0.16mm,中央±8mm环带内圆弧的圆度误差约为5μm,圆周跳动误差约为2μm,截面轮廓圆心轴向位置相对偏差为0.008mm。根据检测结果,进行了大口径复杂非球面磨削实验,得到的元件面形P-V值为4.62μm,RMS值优于0.7μm,满足工程的实际需求。     

圆弧形砂轮精密修整及其声发射在线监测技术

针对球面、非球面及自由曲面超精密磨削加工用圆弧形金刚石砂轮难以精密修整的问题,提出基于旋转绿碳化硅（GC）磨棒的端部在位精密修整方法及修整过程的声发射在线监测技术。基于圆弧形金刚石砂轮的结构特性,制订圆弧形金刚石砂轮的在位精密修整与修整过程的声发射在线监测技术方案。依据修整与在线监测方案,对D64圆弧形金刚石砂轮进行修整实验及其声发射信号采集,修整后跳动误差小于10μm,比修整前减小30μm左右,砂轮精度显著提高。利用声发射信号均方根值获取砂轮修整结束的特征预警阈值,实现了旋转GC磨棒端部在位精密修整过程的在线监测以及修整结束时间的准确判断,可以有效提高球面非球面磨削加工过程的效率。     

基于金刚石微粉烧结棒的超硬砂轮修整试验研究

对金刚石微粉烧结棒修整树脂结合剂金刚石砂轮进行了试验研究.以反映砂轮平面度的端面跳动和径向跳动作为修整效率的评价依据,通过对主轴转速、砂轮组织参数、修整棒进给速度3个方面进行对比试验,得出了以下结论:低主轴转速下修整棒对金刚石砂轮的修整效率较高,砂轮参数对修整效率的影响很小以及修整棒进给速度与修整效率呈非线性关系.     

IN SITU TRUING/DRESSING OF DIAMOND WHEEL FOR PRECISION GRINDING

An application for achieving on-machine truing/dressing and monitoring of diamond wheel is dealt with in dry grinding. A dry electrical discharge （ED） assisted truing and dressing method is adopted in preparation of diamond grinding wheels. Effective and precise truing/dressing of a diamond wheel is carried out on a CNC curve grinding machine by utilizing an ED assisted diamond dresser. The dressed wheel is monitored online by a CCD vision system. It detects the topography changes of a wheel surface. The wear condition is evaluated by analyzing the edge deviation of a wheel image. The benefits of the proposed methods are confirmed by the grinding experiments. The designed truing/dressing device has high material removal rate, low dresser wear, and hence guarantees a desired wheel surface. Real-time monitoring of the wheel profile facilitates determining the optimum dressing amount, dressing interval, and the compensation error.     

Experimental study on fabrication and evaluation of micro pyramid-structured silicon surface using a V-tip of diamond grinding wheel

A mechanical fabrication of micro pyramid-structured silicon surface is proposed using crossed grooving with a 60° V-tip of diamond grinding wheel. It can obtain high form-accuracy, good surface quality and efficient productivity in contrast to laser machining and etching, and also assure a high aspect ratio in contrast to other mechanical processes. In order to describe its micro-structured topography, a white-light interferometer was employed, and its measured point cloud was matched using an Iterative Closest Point (ICP) algorithm. In micro grinding, a novel CNC mutual-wear truing was first developed to sharpen the wheel V-tip; then, the effects of microscopic wheel topography, silicon crystal-orientation and grinding parameter were investigated on ground micro-topography, truing ratio and material removal ratio; finally, its form-accuracy, pyramid top radius, groove tip radius, surface roughness and aspect ratio were evaluated. It is shown that better microscopic grain protrusion topography on wheel V-tip produces much larger material removal ratio and much better micro-structured topography in micro grinding, but it leads to much less truing ratio in finer GC truing. In micro grinding, silicon crystal-orientation has little effect on micro-structured topography due to diamond crystal-orientations that are randomly distributed on wheel V-tip. Although the micro pyramid-structured form error is only about 3.4 μm, its V-groove bottom and pyramidal top have very large form errors (23.1-47.9 μm) due to the sharpness of wheel V-tip and the frangibility of micro pyramid top. On increasing feed speed, its pyramid top radius decreases and its groove tip radius slightly increases, ultimately leading to an increase in aspect ratio, whereas its surface quality descends. It is concluded that the micro-pyramid arrays may be precisely patterned on silicon surface using a SD600 wheel with crossed tool paths, on-machine V-tip truing and the depth of cut in 1 μm.     

Form-truing error compensation of diamond grinding wheel in CNC envelope grinding of free-form surface

In computer numerical control (CNC) grinding of free-form surface, an ideal arc profile of trued diamond grinding wheel is generally employed to plan 3D tool paths, whereas its form-truing errors greatly influence the ground form accuracy. A form-truing error compensation approach is proposed by using an approached wheel arc profile to replace the previously designed ideal one. The objective is to directly compensate the trued wheel arc-profile errors. It may avoid the time consumption of traditional approach that compensates the measured coordinate point errors of workpiece to an iterative grinding operation. First, the 3D tool path surface was constructed to plan the 3D tool paths. Second, the CNC arc truing of grinding wheel was conducted to analyze the form-truing error distribution relative to the applied wheel arc profile. Then, the form-truing error compensation was carried out in CNC envelope grinding. Finally, the iterative closest point (ICP) algorithm was used to match the measured coordinate points of workpiece to ideal free-form surface. It is shown that the 3D tool path surface constructed is practicable to plan arbitrary 3D tool paths for the form-truing error compensation. The ICP matching may be used to investigate 3D ground form error distribution. It is confirmed that the form-truing error compensation can directly improve the 3D ground form accuracy. It may decrease the 3D ground form error by about 20% when the 2D form-truing error is reduced by about 58% using the same truing conditions for CNC grinding.     

铸铁基金刚石球头砂轮精密修整技术

针对小直径、深凹非球光学曲面超精密磨削中使用的铸铁基金刚石球头砂轮,提出了一种基于电火花加工原理的精密在位修整方法。只要改变工具电极直径,即可对不同直径的球头砂轮进行修整。实验表明,用该方法修整出的铸铁基金刚石球头砂轮具有良好的精度和高等微刃群,可很好地满足小直径、深凹光学零件的超精密磨削加工要求。     

ROTARY TRUING OF VITREOUS BOND DIAMOND GRINDING WHEELS USING METAL BOND DIAMOND DISKS

Experiments on rotary truing of vitreous bond diamond grinding wheels were conducted to investigate the effects of truing speed ratio, type of diamond in the metal bond truing disks (synthetic versus natural), and diamond grit size in the grinding wheel on the wear of truing disk and on the cylindrical grinding of zirconia. Similar to G-ratio, a new parameter called D-ratio is defined to quantify the wear rate of the diamond truing disks. Experimental results show that, under the same truing condition, the truing disk with blocky, low friability synthetic diamond has a higher D-ratio than the truing disk with natural diamond. Diamond wheels trued by the disk with synthetic diamond also generate lower grinding force and rougher surface finish. High truing disk surface speed, 1.8 times higher than the surface speed of the grinding wheel, was tested and did not show any improvement in D-ratio. This study indicates that μm-scale precision form truing of the vitreous bond diamond wheel is difficult due to excess wear of the metal bond diamond truing disk.