ELID磨削砂轮表面氧化膜状态的表征

在线电解修整磨削(ELID)是一种电化学加工技术,可在磨削过程中对铸铁基砂轮进行连续修整,非常适合硬脆材料的超精密镜面加工.在ELID磨削过程中,砂轮表面氧化膜的状态对ELID磨削影响重大,在磨削过程中维持良好的氧化膜状态是获良好表面质量的前提保证.本文通过粘附性实验,建立了氧化膜的状态归一化模型,利用在ELID磨削过...     

Grinding of aluminium silicon carbide metal matrix composite materials by electrolytic in-process dressing grinding

The grinding cost of metal matrix composite materials is more due to low removal rates and high rates of wear of super abrasive wheels. This electrolytic in-process dressing (ELID) technique uses a metal-bonded grinding wheel that is electrolytically dressed during the grinding process for abrasives that protrude continuously from super abrasive wheels. This research carries out ELID grinding using various current duty ratios and conventional grinding of 10% SiC_p reinforced 2,124 aluminium composite materials. Normal forces and tangential forces are monitored. Surface roughness of the ground surface, Vickers hardness numbers and metal removal rate (MRR) are measured. The results show that the cutting forces in the ELID grinding are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of grinding wheel and are less than conventional grinding forces. A smoother surface can be obtained at high current duty ratio in ELID grinding. The micro-hardness is reduced at high current duty ratio. In ELID, the MRR increases at high current duty ratio. The results of this investigation are presented in this paper.     

SUS304不锈钢ELID镜面磨削正交化实验研究

SUS304不锈钢具有高耐腐耐磨性和良好的综合性能而被广泛应用,但其高韧性和低导热性使传统的SUS304不锈钢磨削或车削工艺存在一定困难。在线电解修整ELID(Electrolytic in-process dressing)磨削技术能有效地用于SUS304不锈钢镜面磨削加工。本文主要对SUS304不锈钢进行ELID镜面磨削正交化实验研究以获得合理的工艺参数。首先利用#325砂轮进行7个影响因素2水平的正交磨削实验,获得初步的优化参数,然后利用#1200砂轮进行3个影响因素2水平的正交镜面磨削实验。通过改变削件砂轮转速、X和Y平台移动速度、进给率和ELID电源件等各种磨削条件,获得优化后的磨削工艺参数,进行了相应的磨削验证,并讨论了工艺参数对磨削特性的影响。研究了不同砂轮磨粒对表面粗糙度的影响,使用#8000金刚石砂轮对SUS304不锈钢镜面磨削,获得表面粗糙度Ra=3.6 nm。     

A study on wear mechanism and wear reduction strategies in grinding wheels used for ELID grinding

Metal-bonded superabrasive diamond grinding wheels have superior qualities such as high bond strength, high stability and high grindability. The major problems encountered are wheel loading and glazing, which impedes the effectiveness of the grinding wheel. Electrolytic in-process dressing (ELID) is an effective method to dress the grinding wheel during grinding. The wear mechanism of metal-bonded grinding wheels dressed using ELID is different form the conventional grinding methods because the bond strength of the wheel-working surface is reduced by electrolysis. The reduction of bond strength reduces the grit-depth-of-cut and hence the surface finish is improved. The oxide layer formed on the surface of the grinding wheel experiences macrofracture at the end of wheel life while machining hard and brittle workpieces. When the wheel wear is dominated by macrofracture, the wheel-working surface is free from loaded chips and worn diamond grits. When the oxide layer is removed from the wheel surface, the electrical conductivity of the grinding wheel increases, and that stimulates electrolytic dressing. The conditions applied to the pulse current influence the amount of layer oxidizing from the grinding wheel surface. Longer pulse ‘on’ time increases the wheel wear. Shorter pulse ‘on’ time can be selected for a courser grit size wheel since that type of wheel needs high grinding efficiency. Equal pulse ‘on’ and ‘off’ time is desired for finer grit size wheels to obtain stable and ultraprecision surface finish.     

全陶瓷球轴承套圈沟道精密磨削用砂轮修整试验

为提高金刚石圆弧砂轮外缘轮廓精度,减少全陶瓷球轴承套圈沟形误差,采用金刚石碟片对树脂基金刚石圆弧砂轮进行修整;对比修整前后砂轮的表面形貌及套圈沟形误差,验证砂轮的修整效果.修整后砂轮表面出现光泽,露出表面的金刚石磨粒明显增多,部分金刚石磨粒破碎,形成新切削刃或脱落,增大容屑空间;修整前沟形误差的平均值为5.823μm,...     

基于砂轮径向振动主动控制的ELID内圆磨削

在线电解修整(ELID)磨削过程中砂轮表面会生成一层具有一定厚度的氧化膜,其刚度远小于工件及砂轮结合剂的刚度,可以有效衰减磨削过程中的振动。将ELID技术应用到无心内圆磨削中,通过调节电解参数来改变氧化膜的状态,进而对砂轮径向振动进行控制。通过试验研究了电解参数的改变对砂轮径向振动的影响规律,并基于此规律设计了控制器,对磨削过程中的砂轮径向振动进行了主动控制磨削试验。试验结果表明,该控制器可以将磨削过程中的砂轮径向振动控制在设定值附近,维持ELID磨削的稳定。在实际的ELID内圆磨削中,可以先将砂轮径向振动控制在较高值,以实现较大的材料去除率;一段时间后再将砂轮径向振动控制在较低值,以提高工件表面质量。     

ELID 磨削工艺控制研究

砂轮表面氧化膜的形成规律与特性对ELID超精密磨削质量有着重要的影响。研究在ELID磨削中氧化膜的形成规律,基于电化学基本原理,模拟砂轮表面氧化膜形成过程,并分析金刚石砂轮电解预修整过程中氧化膜的生长规律。在此基础上,总结出控制氧化膜生长的几个主要因素之间的关系,分析和确定氧化膜生长厚度与电压之间的关系,应用循环结构编程设计实现ELID磨削工艺控制。     

Cylindrical grinding of bearing steel with electrolytic in-process dressing

Cylindrical surfaces are increasingly utilized in various areas, and related high-efficiency and high-quality fabricating technologies are of great importance and significant benefit to modern industry. To provide fundamental knowledge for the bearing industry, studies have been conducted on the use of cast-iron-bonded cubic boron nitride (cBN) superabrasive wheels, based on electrolytic in-process dressing (ELID) technique for realizing high-efficiency grinding of steel cylindrical workpieces. Therefore, in this investigation, experiments were carried out on an ordinary cylindrical grinder with a hydrodynamic spindle, and straight type grinding wheels of different grit sizes were used. The effects of grit sizes on surface roughness as well as waviness, roundness, and surface stress were evaluated in both the traverse and plunge grinding modes. Comparison of ELID grinding with other processes was also carried out. Mirror surface grinding of different materials was achieved with the #4000 CIB-cBN wheel. ELID grinding was confirmed to induce compressive stress and to be more cost effective for small batch production of larger components when it works in the traverse mode.     

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。     

超声ELID复合内圆磨削时电参数对氧化膜的影响

通过Labview对试验中电压电流的测试,用VHX-2000超景深显微镜对氧化膜进行观测,分析了超声ELID复合磨削电参数与砂轮表面氧化膜之间的关系。研究结果表明,电参数的选择决定了砂轮结合剂发生电解反应溶解去除的速度以及砂轮表面生成氧化膜的厚度,进而影响砂轮的磨削性能和工件的磨削质量。     

Experimental study of wheel wear in electrolytic in-process dressing and grinding

Profile accuracy of components ground with ultra-precision machine tools is primarily dependent on wheel wear. Quantitative analysis of wheel wear is therefore an important aspect for precision grinding with electrolytic in-process dressing (ELID). In this paper, wheel wear is measured from ELID grinding experiments with different dressing and machining parameters. The grinding forces and dressing current characteristics of the experiments are also compared. Based on the results, a benchmark function is defined for wheel wear rate. A relation for identifying insufficient dressing from sufficient dressing for particular machining conditions is also identified. It is found that insufficient dressing produces pitting and/or arcing on the wheel surface, and wheel wear can be linearly correlated to ELID grinding conditions when the wheels are sufficiently dressed.     

Research on surface integrity of grinding Inconel718

Inconel718 is widely used in the aerospace industry; the finished surface quality has significant effect on service performance of component. The surface integrity in grinding Inconel718 respectively by using a vitrified bond single alumina (SA) wheel and a resin cubic boron nitride (CBN) wheel were investigated. First, effects of different grinding parameters on grinding temperature and grinding force and grinding chips feature by using a SA and a CBN wheel respectively were investigated. Then, the surface roughness and topography by using a SA and a CBN wheel through single factor experiment were compared, and in the grinding parameters range of the present study, the better surface can be obtained by a SA wheel. Finally, surface integrity by using a SA wheel and the different grinding depth was studied and analyzed by the grinding temperature and the grinding force. It was possible to conclude that better surface can be achieved by using a SA, and taking a _p?=?0.005 mm, v _w?=?16 m/min, v _s?=?25 m/s for grinding Inconel718. In this grinding case, the surface roughness was Ra0.112 μm, the surface residual stress was +700Mpa, and the surface hardness was 440 HV; the depth of residual stress layer was 40～60 μm, the depth of softened layer was 30～40 μm and the depth of plastic deformation layer was 10～15 μm.     

ELID磨削氧化膜厚度测量方法研究

在ELID磨削原理的基础上,分析了ELID磨削过程中氧化膜的生成和作用机理以及氧化膜的生长规律;综合评述了氧化膜厚度的离线测量方式以及用ELID磨削加工过程中的电压电流值的大小间接表征氧化膜的状态的最新进展。同时提出了基于LabVIEW开发平台,利用激光位移传感器和电涡流位移传感器的组合在线直接测量氧化膜的厚度的方法。     

ELID超精密磨削钢结硬质合金及其表面质量分析

运用铁基结合剂金刚石砂轮与专用高频脉冲电源相配合,对钢结硬质合金（ＧＴ３５）进行在线电解修整（ＥＬＩＤ）精密磨削。分析了ＥＬＩＤ超精密镜面磨削异相非均质材料钢结硬质合金表面的磨削机理,并通过原子力显微镜对其表面进行了微观表面形貌的分析。     

单层钎焊金刚石砂轮的精密修整及效果评价

单层钎焊金刚石砂轮作为一种新型的磨削工具,具有磨粒固结强度高、磨粒出露大、容屑空间大等优点,比较适合高效率大切深的强力磨削,然而这种工具对高性能的脆性材料的精密磨削却比较困难。本文通过两种精密的修整工艺,使得加工表面质量大大提高。通过观察砂轮磨粒形态的变化可知,磨粒在修整过程中存在有磨损钝化、破碎、表面粘附等现象;通过对砂轮轮廓的激光测量可知,砂轮的磨粒等高性在修整过程中是明显改善的。通过修整磨粒粒径300μm的钎焊砂轮磨削氧化锆的表面粗糙度达到了Ra0.2μm。     

Grinding damage of BK7 using copper-resin bond coarse-grained diamond wheel

Coarse-grained wheels can realize high efficient grinding of optical glass. However, the serious surface and subsurface damage will be inevitably introduced by the coarse-grained wheels. In this paper, the grinding damage of a copper-resin bond coarse-grained diamond wheel with grain size of 150μm was investigated on optical glass BK7. The wheel was first properly trued with a metal bond diamond wheel, then pre-dressing for the wheel and grinding experiments are carried out on a precision grinder assisted with electrolytic in process dressing (ELID) method. The surface roughness (Ra) of ground surface was measured using an atomic force microscope (AFM) and the surface topography were imaged by a white light interferometer (WLI) and the AFM. The subsurface damage level of ground surface was evaluated by means of both MRF spot method and taper polishing-etching method, in term of the biggest depth of subsurface damage, distribution of micro defects beneath the ground surface, the cluster depth of subsurface damage, relationship between subsurface damage (SSD) and PV surface roughness (SR), propagating distance and pattern of cracks beneath the ground surface. Experimental results indicate that a well conditioned copper-resin bond coarse-grained diamond wheel on a precision grinder can generate good surface quality of Ra less than 50nm and good subsurface integrity with SSD depth less than 3.5ε for optical glass BK7.     

ELID磨削氧化膜控制方案的设计与研究

微处理器为处理控制单元,通过ELID精密磨削技术对金属基砂轮进行在线修整,改变砂轮氧化膜厚度,从而调整ELID磨削状态.该方案自动处理数据,判断磨削膜厚状态,改变电解电源参数,使砂轮始终保持锋利状态.此方法实现磨削过程无人控制,砂轮连续自动修整,消除传统磨削加工停机修整砂轮的弊端,提高磨削效率,减少砂轮过快损耗.     

Efficient dressing of the wheel in ELID grinding by controllable voltage with force feed back

Electrolytic in-process dressing (ELID) grinding is a new method for achieving ultraprecision surface on hard and brittle materials. In ELID grinding, pulsed direct current voltage is applied on the metal-bonded diamond wheels to ensure constant protrusion of sharp cutting grits throughout the grinding cycle. The peak dressing voltage is kept constant irrespective of the wheel sharpness in conventional ELID grinding, which may lead to overdressing of the grinding wheel. Grinding force ratio (which is also known as K value) is an indicator for the grit sharpness. In this paper, a new approach of wheel dressing has been proposed where the peak dressing voltage is varied according to the change in the K value during grinding. A Kistler three-component dynamometer has been used to monitor the grinding force ratio in real time for this purpose. The methodology to implement the new “dressing-on-demand” concept has been discussed thoroughly in this paper. The experimental comparison with the conventional ELID grinding has also been carried out to prove the advantages of the proposed system.     

电镀金刚石砂轮高效精密修整及熔融石英磨削试验研究

大尺寸光学玻璃元件主要采用细磨粒金刚石砂轮进行精密/超精密磨削加工,但存在砂轮修整频繁、工件表面面形精度难以保证、加工效率低等缺点。采用大磨粒金刚石砂轮进行加工则具有磨削比大、工件面形精度高等优点,然而高效精密的修整是其实现精密磨削的关键技术。采用Cr12钢对电镀金刚石砂轮(磨粒粒径151 μm)进行粗修整,借助修整区域聚集的热量加快金刚石的磨损,可使砂轮的回转误差快速降至10 μm以内。结合在线电解修锐技术,采用杯形金刚石修整滚轮对粗修整后的电镀砂轮进行精修整,砂轮的回转误差可达6 μm以内,轴向梯度误差由6 μm降至2.5 μm。通过对修整前后的金刚石砂轮表面磨损形貌成像及其拉曼光谱曲线分析了修整的机理。对应于不同的砂轮修整阶段进行熔融石英光学玻璃磨削试验,结果表明,砂轮回转误差较大时,工件材料表面以脆性断裂去除为主;随着砂轮回转误差和轴向梯度误差的减小,工件表面材料以塑性去除为主,磨削表面粗糙度为Ra19.6 nm,亚表层损伤深度低至2 μm。可见,经过精密修整的大磨粒电镀金刚石砂轮可以实现对光学玻璃的精密磨削。     

ELID 超精密磨削砂轮表面氧化膜形成过程的建模和仿真

砂轮表面氧化膜的形成规律与特性对ELID超精密磨削质量有着重要的影响。为了研究在ELID磨削中氧化膜的形成规律,基于电化学基本原理,建立了砂轮表面氧化膜形成过程的一般模型,并对金刚石砂轮电解预修整过程中氧化膜的生长过程进行了仿真。在此基础上,对控制氧化膜生长的主要因素进行了理论分析。为了验证模型和仿真结果的正确性,采用与仿真过程同样的控制参数,对氧化膜的生长特性进行了实验研究。结果表明仿真结果与实验结果基本吻合。