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。     

金属基圆弧形金刚石砂轮在位精密修整实验研究

金属基圆弧形金刚石砂轮具有耐磨性好、结合强度高、寿命长等优点,广泛的应用于非回转、非对称大尺寸光学自由曲面的精密磨削中,但是,金属基体砂轮在位精密修整困难。基于此,采用旋转GC磨棒在位精密修整法,提出了金属基圆弧形金刚石砂轮的进给补偿在位精密修整策略,并在超精密机床上搭建在位修整系统,对D46金属基圆弧形金刚石砂轮进行了修整实验,同时对修整前后的砂轮轮廓误差进行了在位测量,最后采用超景深显微镜和Zygo白光干涉仪对修整后砂轮表面的金刚石磨粒和轮廓形貌进行了观察。结果表明,D46金属基圆弧形砂轮的修整效果明显,验证了本文提出的金属基圆弧形砂轮进给补偿修整策略的正确性和可操作性,实现了金属基圆弧形金刚石砂轮的在位精密修整。     

基于多层钎焊金刚石砂轮在线电解修整技术的超细晶硬质合金精密磨削研究

利用模压成型技术和真空钎焊技术制备出了磨粒把持力大、力学性能优良的多层钎焊金刚石砂轮;采用在线电解修整技术促使磨钝的磨粒及时脱落,使砂轮在磨削过程中始终保持锋利性;并开展了基于多层钎焊金刚石砂轮在线电解修整技术的超细晶硬质合金精密磨削试验。试验结果表明：在相同磨削条件下,多层钎焊砂轮在线电解修整磨削力较无修整时的磨削力下降了33.7%～57.9%;多层钎焊砂轮在线电解修整磨削技术能有效提高加工表面质量。当进给速度为30 mm/s,磨削深度为15 μm时,无电解磨削加工表面粗糙度为0.35 μm,而在线电解修整磨削表面粗糙度仅为82.1 nm;多层钎焊砂轮在线电解修整磨削残余应力仅为无电解磨削时的38.2%～49.5%。且在线电解修整磨削表面完整性较好,没有出现表面/亚表面裂纹等相关缺陷,可实现超细晶硬质合金等难加工材料的高效精密加工。     

基于信息融合的精密磨削砂轮磨损状态在线识别方法研究

高质量非球面光学元件批量制造是目前精密磨削技术力求实现的目标。为了提高非球面光学元件精密磨削的加工效率,必须在加工过程中动态识别砂轮磨损状态,在砂轮接近或达到寿命周期时对其进行修整。寻求一种经济可行的方式,实现砂轮寿命周期在线评估,利用声发射、砂轮振动、磨削力等多种类型加工过程信号,提取和选择能够全面、灵敏反应砂轮磨损状态的特征,基于Dempster-Shafer证据理论,进行多源信息融合,实现精密磨削砂轮磨损状态在线识别。     

垂直式超硬砂轮圆弧修整器设计与砂轮修整

针对圆弧形超硬砂轮修整难度大、修整精度低的问题,对树脂结合剂圆弧形金刚石砂轮进行了精密修整研究。设计制造了一种垂直式超硬砂轮圆弧修整器,通过修整试验研究了不同粒度的圆弧形砂轮在修整前后表面粗糙度、弧形精度、圆度、表面形貌的变化情况。砂轮修整前后对氮化硅陶瓷轴承套圈沟道进行了磨削,并测量了磨削后的轴承套圈沟形精度。研究结果表明：相比修整前,修整后砂轮表面粗糙度平均值由1.731 8 μm减小至0.772 4 μm,减小了55.4%;弧形精度平均值由33.604 7 μm减小至8.527 6 μm,减小了74.6%,修整后4个砂轮的弧形精度更加稳定,且随着砂轮粒度的减小,弧形精度略有减小趋势;砂轮圆度平均值由43.721 μm减小至18.002 μm,减小了58.8%,修整使大量新的磨粒露出。所设计的垂直式超硬砂轮圆弧形修整器可对圆弧砂轮进行精密修整,可改善圆弧形砂轮的弧形精度及圆度,修整后砂轮磨削的轴承套圈沟形精度得到了大幅提高。     

基于声发射监测的金刚石砂轮修整技术研究

建立完善的金刚石砂轮修整的声发射监测系统,利用声发射信号可直观反映出金刚石砂轮实际修整情况.通过分析计算砂轮在整形过程中声发射信号的标准差值可定量分析出砂轮实际修整效果,实验中使用电容传感器测量整形前后砂轮表面外形,测量结果证明了声发射监测系统在金刚石砂轮修整中的有效性.     

砂轮磨钝监测及修整

利用声发射(AE）信号归原处理法对砂轮磨钝程度进行监测，在此基础上开发了砂轮磨钝监测及自动修整系统。该系统可以对小批量、多品种工件磨削过程中砂轮钝化进行有效的监测，采用的CNC砂轮自动修整器能够解决多种类型成型砂轮的修整，具有一定的通用性和实用性，能实现磨削砂轮监测、修整过程的自动化和智能化。     

应用超硬大磨粒金刚石砂轮实现BK7光学玻璃的超精密磨削

首先以91μm磨粒杯形铜基金刚石砂轮作为修整器并结合砂轮在线电解修锐技术(ELID,Electrolytic in- process dressing)对151μm磨粒电镀镍基单层金刚石砂轮进行精密高效的修整。在最佳的修整参数下,同时应用测力仪对两个砂轮间磨削力进行监测,并应用共轴光学位移检测系统对砂轮表面状态进行在位监测,151μm砂轮的回转误差被减小至1～2μm范围,同时砂轮上所有金刚石磨粒被修整出平坦表面并拥有恒定的圆周包迹,此时砂轮达到最佳工作状态。然后应用被良好修整的砂轮对光学玻璃BK7进行磨削加工。磨削试验结果和亚表层完整度评价结果表明新开发的大磨粒金刚石砂轮修整技术的可行性,也验证大磨粒金刚石砂轮只要经过精密修整是可以应用于光学玻璃的延展性超精密磨削加工的,并能实现纳米级的表面粗糙度,显示出大磨粒金刚石砂轮在加工难加工材料和硬脆材料中的良好应用前景。     

大直径凸弧金刚石砂轮精密修整工艺研究

针对大直径凸弧金刚石砂轮硬度高、表面形貌复杂、修整难度大以及修整弧形精度低的问题,提出了一种应用于大直径凸弧金刚石砂轮立式精密挤压修磨的砂轮修整方法,设计研发了大直径超硬凸弧砂轮立式在线精密修整装置。其基本原理是高强度金刚石凸弧修整轮自转并进行立式圆弧摆动形成约束圆弧面,通过金刚石凸弧修整轮与金刚石砂轮磨粒之间产生的挤压微磨削作用对金刚石砂轮进行精密修磨成型。对基本修整工艺规律进行了研究分析与初步试验探索。通过金刚石砂轮修整前后磨削全陶瓷球轴承内圈的沟道精度对比分析表明,该砂轮修整理论、修整装置与修整工艺能够实现大直径凸弧微粒度金刚石砂轮精密修整,并达到所需修整的精度要求。     

基于小波分析和GA-SVM的金刚石 砂轮磨损的声发射监测研究

针对工程陶瓷磨削中金刚石砂轮磨损状态判别准确度不高的问题,在部分稳定氧化锆陶瓷金刚石砂轮精密磨削的声发射智能监测实验中,在深入研究部分稳定氧化锆陶瓷磨削机理的基础上,对磨削声发射信号进行了5层离散小波分解。研究结果表明:金刚石砂轮磨损后,磨削声发射信号小波分解系数的有效值和方差,以及声发射信号小波能谱系数在低频率段都有所增大;利用部分稳定氧化锆磨削声发射信号的小波能谱系数或小波分解系数的有效值和方差值的组合,作为判别金刚石砂轮磨损状态的特征值,采用基于遗传算法支持向量机对金刚石砂轮的磨损状态判别准确度达100%,判别准确度明显优于BP神经网络方法。     

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.     

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

Abstract

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.     

Wear of the blade diamond tools in truing vitreous bond grinding wheels: Part II. Truing and grinding forces and wear mechanism

Truing and grinding forces and the wear mechanism of particle and rod diamond blade tools used to generate precise and intricate forms on rotating vitreous bond silicon carbide grinding wheels are presented. A Hall effect sensor was used to measure the change of grinding spindle power during truing and grinding. A signal processing procedure was developed to identify individual truing passes and to extract the average, peak-to-valley, and standard deviation of the variation of truing force for each pass. The truing force data and SEM micrographs of worn surfaces on blade tools reveal micro- and macro-fracturing of the diamond. The attritious and erosion wear of the diamond rod and particle, erosion of the metal bond, and pulling-out of the diamond particle are also identified. Grinding force data shows that, for the same truing parameters, a wheel trued by the rod diamond blade tool has higher grinding forces than one trued by a particle diamond blade tool.     

铸铁基超硬磨料砂轮的电化学机械整形工艺及其作用机理

进行了失基超细粒度金刚石／ＣＢＮ砂轮的精密电化学机械整形试验研究,并深入分析了电解液成分、电解电流、油石么向进给量等因素对整形效率和整形精度的影响规律,阐明了电化学机械整形的作用机理。     

光学自由曲面反射镜模芯的镜面成型磨削

采用精密修锐修整的圆弧形粗金刚石砂轮在CNC精密磨床上进行了数控成型磨削加工,实现了高效镜面磨削。分析金刚石砂轮圆弧形轮廓的成型修整原理,建立了圆弧形修整的数控模式。通过建立曲面数控成型磨削的行走轨迹算法,实现了自由曲面的圆弧包络成型磨削加工。分析了磨削工艺参数和砂轮出刃形貌参数与超光滑表面形成的作用机制,进行了镜面磨削试验并检测表面微观形貌和粗糙度,分析实现镜面磨削的脆/塑性磨削转换机理。理论分析表明,降低砂轮行走速度,提高砂轮转速以及改善出刃形貌可以获得纳米级粗糙度的超光滑磨削表面。试验结果显示,先将砂轮修锐修整再控制砂轮行走速度小至15 mm/min时,表面粗糙度小于10 nm以下,且微观加工表面没有发生脆性破坏,形成镜面。加工高速钢自由曲面时,面形误差(PV值)可以达到10 μm以下,表面粗糙度R_a可以达到约16 nm。实验结果表明:利用数控技术和粗金刚石砂轮可以实现自由曲面模芯的高效镜面磨削加工,保证了高精度的光学自由曲面反射镜注塑模芯。     

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。     

基于纳米进给铸铁基砂轮电火花精密整形研究

阐述基于图形化编程语言Lab VIEW的数据采集系统,该系统能够实时显示、记录、分析各种实验信号,是金属基金刚石砂轮的电火花整形技术的研究手段和研究基础.根据电火花加工原理,通过一系列实验,借助于数据采集系统采集整形过程中的电压和电流,总结了铸铁结合剂金刚石砂轮的电火花整形规律.采用最小进给量为10 nm的微进给工作台,实现了基于纳米进给的电火花整形,使铸铁结合剂砂轮达到了精密磨削的要求.     

Wear mechanism of metal bond diamond wheels trued by wire electrical discharge machining

The stereographic scanning electron microscopy (SEM) imaging was used to investigate the wear mechanism in wire electrical discharge machining (EDM) truing of metal bond diamond wheels for ceramic grinding. A piece of the grinding wheel was removed after truing and grinding to enable the examination of wheel surface and measurement of diamond protrusion heights using a SEM and stereographic imaging software. The stereographic SEM imaging method was calibrated by comparing with the profilometer measurement results. On the wheel surface after wire EDM truing and before grinding, some diamond grain protruding heights were measured in the 32 μm level. Comparing to the 54 μm average size of the diamond grain, this indicated that over half of the diamond was exposed. During the wire EDM process, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruded in the gap between the wire electrode and wheel. These protruding diamond grains with weak bond to the wheel were fractured under a light grinding condition. After heavy grinding, the diamond protrusion heights were estimated in the 5–15 μm range above the wear flat. A cavity created by grinding debris erosion wear of the wheel bond could be identified around the diamond grain.