金属结合剂金刚石成型砂轮电火花修整方法研究

对金属结合剂金刚石砂轮的凹圆弧成型电火花修整方法进行深入研究,掌握了金属结合剂金刚石成型砂轮的电火花修整工艺,并对砂轮加工电极的材料及形状、最小火花间隙、最大加工参数作了深入分析,确定条形电极为高精度砂轮加工的最佳方式。选定铜钨合金作为金属结合剂金刚石砂轮加工的最佳电极材料,通过研究得到金刚石砂轮的电火花加工工艺参数,成功加工出复杂轮廓金刚石成型砂轮,并用其磨削出高质量的刀具。     

金刚石微粉砂轮电火花修锐微观研究

电火花修锐是金属结合剂粗粒度金刚石砂轮的理想修锐方法，研究表明，金属结合剂金刚石微粉砂轮的电火花修锐表面形貌同金属结合剂粗粒度金刚石砂轮的电火花修锐及磨削法修锐有很大差别。本文从微观角度分析了金属结合剂金刚石微粉砂轮的电火花修锐特性及其影响因素。     

正交磁场对电火花单脉冲放电间隙的影响

通过普通电火花单脉冲放电（EDM）与磁场辅助电火花单脉冲放电（MF-EDM）放电间隙对比试验,分析得出不同磁感应强度、开路电压、放电电容及电极外伸端长度对磁场辅助电火花加工放电间隙的影响规律。试验发现：随着磁感应强度的增大,放电间隙增大;开路电压和放电电容对放电间隙的影响较小;随着电极外伸长度的增大,放电间隙变小。最后对试验数据进行部分析因分析,得出磁场辅助电火花加工中影响放电间隙的主要因素为磁感应强度、电极外伸长度及其交互耦合作用。     

双电极接触放电法在金属结合剂CBN砂轮修整中的应用研究

双电极按触放电是一项修整金属结合剂超硬磨料砂轮的新技木。它利用接触放电电蚀原理以达到去除砂轮的金属结合剂而修锐或整形砂轮。本文在论述修整机理的基础上．对其工艺规律进行了系统的分析和总结．     

微细电火花加工机床关键技术

研制开发两台高精度、高性能,具有自主知识产权的微细电火花加工机床,并对微细电火花加工机床的几个特有关键技术进行了深入研究.基于压电陶瓷的宏微伺服进给系统能实现分辨率为3.42 nm的微进给,并且能实现振动式进给,以改善微细电火花加工的间隙状态,提高微细电火花的加工效率和加工质量.结合块电极反拷与线电极反拷的微细工具电极反拷系统,可高效高精度地现场制作微细电极,电极直径最小可达4 μm.基于多传感器信息融合技术的放电间隙状态监测技术,能很好地解决微细电火花加工间隙状态的监测与识别问题.RC脉冲电源不存在维持电压现象,这一最新发现为降低单脉冲放电能量难题提供一个新的解决途径,使得基于RC方法开发的超微能脉冲电源的单脉冲放电能量最小降至皮焦级,为微细电火花加工奠定了良好的基础.最后的微细电火花加工试验表明,所开发的微细电火花加工机床性能稳定,且加工质量良好,尤其适合加工孔径为50～200 μm的微细孔.     

超声复合微细电火花加工机理与试验

微结构电火花加工短路、断路或电弧放电作用,降低加工效率及精度。提出将超声频振动与微细电火花加工复合,利用电极与工件之间的超声频相对运动,产生规则的、参数可控的微细脉冲放电;构造、完善超声复合微细电火花试验系统,进行微结构超声复合电火花加工试验,有效避免短路、断路及电弧脉冲,有效提高加工精度与效率。TG662     

电火花整形金刚石微粉砂轮的工艺试验研究

针对ELID磨削轴承钢内圆存在的金属结合剂超硬磨料砂轮整形难题,采用电火花整形技术对金刚石微粉砂轮进行工艺试验研究。在单脉冲放电能量理论指导下,进行正交试验探究脉冲电流、放电电压及占空比对砂轮表面三维粗糙度的影响及其最优参数组合。研究结果表明在脉冲电流10A,放电电压70 V,占空比20%的最佳工艺参数下进行电火花精密整形得到砂轮表面三维粗糙度的评价参数S_P、S_Q、S_(SK)及S_(KU)分别为13.05μm、4.89μm、-0.35、5.307和得到精度为4.18μm的砂轮圆度。最后将电火花精密整形后的W40粒度金刚石砂轮应用在ELID磨削轴承钢内圆中得到表面粗糙度为96 nm的加工表面。     

磁场辅助电火花加工放电间隙数学模型的建立

与微细电极正交布置的磁场通过影响放电通道,扩大放电间隙改善放电环境并且增大放电能量,有效提高了电火花加工效率。为了预测及调控磁场辅助电火花加工(MF-EDM)的放电间隙,采用部分析因试验设计方法,应用数学优化分析软件1stOpt,基于正交磁场辅助单脉冲电火花放电的试验数据进行非线性多项式拟合,建立了放电间隙的数学模型,并通过进一步试验验证模型的可靠性,实际值与估算值误差控制在8%以内。     

一种新型卧式微电火花机床的设计与实验研究

针对微电极制作的效率问题,提出了一种快速在线微电极加工成形的方法,设计了一种新型卧式微电火花机床。该机床由金刚石砂轮超精密在线电极磨削、线电极电火花在线电极磨削共同完成微米级电极的高效精密制作,该机床组成部分还包括基于CCD的在线光学尺寸检测与测量系统、精密运动与进给系统、纳秒级独立式脉冲放电电源与放电状态检测反馈系统组成。在该机床上进行了微电极制作、微小孔加工以及微电火花铣削等实验,加工出直径为15μm微细轴和直径为50μm微小孔。     

辅助侧向吹气法金刚石砂轮激光修锐试验与评价

介绍了辅助侧向吹气法金属结合剂金刚石砂轮的激光修锐试验和简化测力评价方法,计算比较了修锐前后砂轮磨削力、磨削力比和比磨削能,从不同角度说明了辅助侧向吹气法对激光修锐金属结合剂金刚石砂轮的有效性。分析了修锐前后砂轮表面与对应磨削试件表面的微观形貌机理,解释了影响磨削力变化的因素。采用辅助侧向吹气法能够解决金属结合剂砂轮激光修锐中常见的熔化覆盖问题,使砂轮磨削力比同轴吹气法修锐下降5％～7％,激光修锐砂轮的磨削性能得到明显改善。     

基于气中放电辅助修整金刚石砂轮的试验研究

提出了一种新型的基于气中放电辅助金刚石砂轮在线修整法,它把气中火花放电修整法和金刚石笔机械修整法有机结合在一起,能实现光学曲线磨床上金刚石砂轮的高效、高精度、低成本和不得使用任何冷却液的在线修整。采用自制的试验装置在MK9025数控光学曲线磨床上对1A1／T2 200×6×32×4 MBD6 120／140 M75型号的砂轮进行了在线修整试验,得出了一些影响金刚笔磨损率的主要因素:火花放电时热源的能量分布状况、金刚石笔修整时的修整深度、进给量以及电源电压。相同工况下机械修整法和气中放电辅助修整法中金刚石笔的磨损率对比试验结果表明:气中放电辅助修整和机械修整有着不同的材料去除机理,它比一般机械修整更有利于提高金刚石砂轮的修整效率和降低金刚石笔的磨损量。磨削YG8硬质合金工件的试验表明,采用气中放电辅助法修整的金刚石砂轮和新的金刚石砂轮有着相近的磨削能力。     

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.     

On-machine precision preparation and dressing of ball-headed diamond wheel for the grinding of fused silica

In the grinding of high quality fused silica parts with complex surface or structure using ball-headed metal bonded diamond wheel with small diameter,the existing dressing methods are not suitable to dress the ball-headed diamond wheel precisely due to that they are either on-line in process dressing which may causes collision problem or without consideration for the effects of the tool setting error and electrode wear.An on-machine precision preparation and dressing method is proposed for ball-headed diamond wheel based on electrical discharge machining.By using this method the cylindrical diamond wheel with small diameter is manufactured to hemispherical-headed form.The obtained ball-headed diamond wheel is dressed after several grinding passes to recover geometrical accuracy and sharpness which is lost due to the wheel wear.A tool setting method based on high precision optical system is presented to reduce the wheel center setting error and dimension error.The effect of electrode tool wear is investigated by electrical dressing experiments,and the electrode tool wear compensation model is established based on the experimental results which show that the value of wear ratio coefficient K’ tends to be constant with the increasing of the feed length of electrode and the mean value of K’ is 0.156.Grinding experiments of fused silica are carried out on a test bench to evaluate the performance of the preparation and dressing method.The experimental results show that the surface roughness of the finished workpiece is 0.03 μm.The effect of the grinding parameter and dressing frequency on the surface roughness is investigated based on the measurement results of the surface roughness.This research provides an on-machine preparation and dressing method for ball-headed metal bonded diamond wheel used in the grinding of fused silica,which provides a solution to the tool setting method and the effect of electrode tool wear.     

ELECTRICAL DISCHARGE DIAMOND GRINDING OF HIGH SPEED STEEL

A combination of two machining processes (i.e., a hybrid process) has a potential to improve process performance. This paper reports on experimental investigation of the electrical discharge diamond grinding process that combines mechanical grinding with electrical discharge machining. In this process, the workpiece is simultaneously subjected to heating, by electrical sparks bridging the gap between the metallic wheel bonding material and the work, and abrasion by diamond grains. The effect of current, voltage, pulse-on-time and duty factor on the grinding forces and the material removal rate while machining high speed steel workpiece, are investigated. The spark discharges facilitate grinding by thermally softening the work material in the grinding zone, and consequently decreasing the nromal force. It is observed that the material removal rate increases with an increase in current and pulse on-time, while it decreases with an increase in voltage and duty factor. These independent parameters are also found to significantly influence the grinding forces.     

激光与电火花复合修整粗粒度弧形金刚石砂轮试验研究

因受到激光高斯光束特性的影响,辐照在砂轮表面上的光斑大小和激光能量都跟随修整路径变化,难以实现高精度的弧形金刚石砂轮的修整,为此,提出采用激光粗修整和电火花精修整的复合修整方法。先用激光修整高效去除多余磨料层来得到弧形轮廓,再用一高精度弧形电极匹配该轮廓进行电火花修整,得到较高精度的弧形砂轮。在粒度为120的金刚石砂轮上试验修整半径为13 mm的弧形轮廓,最终修整出的弧形轮廓半径为13.006 mm,轮廓误差PV值为10.90 μm。最后,通过磨削氧化铝陶瓷验证了砂轮修整效果。检测磨削工件的弧形轮廓拟合半径为13.012 mm,轮廓误差PV值为11.33 μm。     

Diamond face grinding of WC-Co composite with spark assistance: Experimental study and parameter optimization

Electro-discharge machining (EDM) characteristics of tungsten carbide-cobalt composite are accompanied by a number of problems such as the presence of resolidified layer, large tool wear rate and thermal cracks. Use of combination of conventional grinding and EDM (a new hybrid feature) has potential to overcome these problems. This article presents the face grinding of tungsten carbide-cobalt composite (WC-Co) with electrical spark discharge incorporated within face of wheel and flat surface of cylindrical workpiece. A face grinding setup for electro- discharge diamond grinding (EDDG) process is developed. The effect of input parameters such as wheel speed, current, pulse on-time and duty factor on output parameters such as material removal rate (MRR), wheel wear rate (WWR) and average surface roughness (ASR), are investigated. The present study shows that MRR increases with increase in current and wheel speed while it decreases with increase in pulse on-time for higher pulse on-time (above 100 μs). The most significant factor has been found as wheel speed affecting the robustness of electro- discharge diamond face grinding (EDDFG) process.     

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。     

电火花机械复合磨削技术的研究进展

电火花机械复合磨削集合了机械磨削和电火花加工两种加工工艺,能够提高加工效率和加工质量,广泛应用于导电难加工材料的加工。本文对电火花机械复合磨削机理和研究现状进行了系统阐述,在分析现有研究成果的基础上,针对大口径Si C反射镜非球面成形磨削中存在的加工效率低、砂轮磨损严重等问题,提出了将电火花机械复合磨削应用于大口径Si C反射镜非球面成形磨削加工的观点,以提高其成形加工效率。     

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.     

结合在线电解修锐高效磨削陶瓷密封件研究

本文通过设计制作金属结合剂金刚石磨具，结合电解修锐技术对Al2O3陶瓷密封进行了研磨式磨削实验在实验过程中通过检测磨具表面的磨粒出露高度及陶瓷材料的去除量，评价该磨削工艺在陶瓷材料密封件加工中的应用效果。结果表明，电解修锐可有效地修锐金属结合剂金刚石磨具，在加工过程中使磨具保持良好的切削能力，因此材料去除量较大，加大工时短，陶瓷密封件的加工成本得到控制。