基于灰色关联理论的RB-SiC陶瓷电火花机械复合磨削工艺参数优化

开展反应烧结碳化硅陶瓷电火花机械复合磨削试验，分析砂轮参数、磨削参数以及放电参数对陶瓷表面粗糙度、材料去除率、砂轮磨损率以及法向磨削力的影响规律。结果表明:与普通磨削相比，电火花机械复合磨削能提高RB-SiC陶瓷的材料去除率，且有效降低磨削时的法向磨削力；但过高的放电能量会造成砂轮的严重磨损，导致材料去除率和磨削表面质量降低。基于灰色关联理论和正交试验对工艺参数进行优化，并开展试验对优化结果进行验证。结果表明:优化后的工艺参数能有效提高材料去除率和磨削表面质量，并降低法向磨削力和砂轮磨损率。      

金刚石砂轮的成形方法

为了满足单件小批量地生产用于加工硬质合金螺纹刀具的金属基金刚石成形砂轮的需求,在原有的电火花加工金属基金刚石成形砂轮的方法上提出一种新的成形金刚石砂轮的加工方法。采用实时检测、实时控制和两轴联动全闭环数控系统单刀加工成形石墨电极,再用电火花加工方法加工出成形金刚石砂轮。并通过实验验证了成形石墨电极的加工精度。此方法能够满足单件小批量生产成形金刚石砂轮的需求。     

An experimental study on a novel diamond whisker wheel

This study proposes a novel diamond whisker wheel for grinding of advanced materials. The wheel is designed to have preferable spatial distributions and orientations of diamond whiskers which are prepared using a laser cutting technique. To obtain desirable cutting edge geometries, the whisker edges are formed on a lapping machine with diamond powders. The whisker wheel is used in a machining test on a silicon carbide particulate reinforced aluminum alloy and compared with a tungsten carbide milling cutter. The whisker wheel grinding provides better surface finish and significantly reduced machining force than for milling at the same material removal rate.     

金刚石砂轮修整机脉冲电源的设计与应用

针对传统的电火花金刚石砂轮修整机脉冲电源人机交互方式陈旧、电源主振脉冲抗干扰能力弱、放电效率低及寄生电感严重等的缺点,设计一款电火花脉冲电源。采用三菱PLC作为系统主控制器,选用STC8A8K64S4A12单片机与EPM570T100C5N CPLD可编程逻辑器件作为脉冲主控芯片,并进行电火花脉冲电源的硬件与软件设计。同时制作金刚石砂轮修整机电源样机,以石墨轮为电极,金刚石砂轮为加工工件进行放电加工试验,检验设计的电源加工性能,并与传统电火花金刚石砂轮修整机进行工艺对比试验。结果表明：设计的脉冲电源控制方式简洁,参数设置方便,放电波形抗干扰能力强,不易失真,放电效率较高,加工的金刚石砂轮表面质量较高,成型面颗粒完整度高。     

Study on the grinding of advanced ceramics with slotted diamond wheels

Slotted diamond wheel grinding is a new machining technology. In this paper, an experimental study on the cutting force and the grinding temperature for ceramic face grinding using slotted diamond wheels is presented. Moreover, the empirical relationships related with the material removal rate, the surface roughness, the depth of cut, the wheel speed and the grain size are discussed. With these relationships, a temperature field for face grinding has been built. The work contributes to the fundamental theories for optimal design of slotted diamond wheels.     

聚晶金刚石电火花超声机械复合加工技术研究

聚晶金刚石具有优良的力、热、化学、声、光、电等性能,在现代工业、国防等领域中得到日益广泛的应用。但是,聚晶金刚石硬度高,耐磨性好,其成型加工非常困难,超声电火花机械复合加工技术是一种有效的加工方法。本研究在分析电火花超声机械复合加工原理的基础上,采用青铜结合剂金刚石砂轮实现了聚晶金刚石的超声电火花机械复合加工。实验分析了超声电火花机械复合加工过程工艺参数与加工效果之间的关系,结果表明,脉宽、脉间、峰值电流、超声振幅、开路电压等参数对复合加工过程工艺结果的影响程度较明显。     

超精密晶圆减薄砂轮及减薄磨削装备研究进展

在芯片制程的后道阶段,通过超精密晶圆减薄工艺可以有效减小芯片封装体积,导通电阻,改善芯片的热扩散效率,提高其电气性能、力学性能。目前的主流工艺通过超细粒度金刚石砂轮和高稳定性超精密减薄设备对晶圆进行减薄,可实现大尺寸晶圆的高精度、高效率、高稳定性无损伤表面加工。重点综述了目前超精密晶圆减薄砂轮的研究进展,在磨料方面综述了机械磨削用硬磨料和化学机械磨削用软磨料的研究现状,包括泡沫化金刚石、金刚石团聚磨料、表面微刃金刚石的制备方法及磨削性能,同时归纳总结了软磨料砂轮的化学机械磨削机理及材料去除模型。在结合剂研究方面,综述了金属、树脂和陶瓷3种结合剂的优缺点,以及在晶圆减薄砂轮上的应用,重点综述了目前在改善陶瓷结合剂的本征力学强度及与金刚石之间的界面润湿性方面的研究进展。在晶圆减薄超细粒度金刚石砂轮制备方面,由于微纳金刚石的表面能较大,采用传统工艺制备砂轮会导致磨料发生团聚,影响加工质量。在此基础上,总结论述了溶胶–凝胶法、高分子网络凝胶法、电泳沉积法、凝胶注模法、结构化砂轮等新型工艺方法在超细粒度砂轮制备方面的应用研究,同时还综述了目前不同的晶圆减薄工艺及超精密减薄设备的研究进展,并指出未来半导体加工工具及装备的发展方向。     

超硬磨料砂轮不同介质中电火花修整试验研究

超硬磨料砂轮的电火花修整受到极间放电间隙的限制,采用传统的放电介质条件难以达到粗粒度砂轮的修整要求。为此,结合混粉放电加工机理,提出混粉介质中的电火花修整方法,进行压缩空气、去离子水雾和混粉去离子水雾3种介质及不同放电参数下的放电间隙对比试验研究,并开展金刚石砂轮修整和工件磨削试验。试验结果表明:混粉介质电火花修整的放电间隙最大,能提高粗粒度青铜结合剂金刚石砂轮的修整效率,同时优化砂轮修整后的表面形貌、磨粒突出状况和磨削性能。在开路电压为90 V、峰值电流为13.33 A及占空比为50%的最佳放电参数下,混粉介质的电火花修整效率与前2种介质相比可提高28.2%～50.0%;且加入的SiO₂粉末使砂轮表面的Si元素分布更均匀、含量更高,进而提高其耐磨性。      

Li-Ti铁氧体陶瓷精密磨削的试验研究

铁氧体陶瓷的应用因其表面加工质量难以保证而受到很大限制。本文采用80/100#树脂结合剂金刚石砂轮和W 20石墨白刚玉砂轮对Li-Ti铁氧体陶瓷进行了磨削试验。研究了单位宽度磨削力、表面粗糙度和单位宽度材料去除率随磨削参数的变化规律,观察并分析了铁氧体工件磨削后的表面微观形貌。结果表明:Li-Ti铁氧体的表面粗糙度值可达到Ra0.084μm,实际单位宽度材料去除率达到90%,材料以塑性方式去除;采用上述砂轮可实现铁氧体陶瓷的高效精密磨削。     

Grinding characteristics,material removal and damage formation mechanisms in high removal rate grinding of silicon carbide

Development of advanced ceramics such as silicon carbide has gained significant importance because of their desirable properties. However, their engineering applications are still limited owing to the limitations in developing damage-free and economical machining techniques. It is often desired to increase the machining rate to improve productivity while maintaining the desired surface integrity. The success of this approach, however, requires a fundamental understanding of the material removal and damage formation mechanism in grinding. In this paper, high removal rate grinding of silicon carbide was investigated with respect to material removal and basic grinding parameters using a diamond grinding wheel. The results showed that the material removal was primarily due to the microfracture and grain dislodgement under the grinding conditioned selected. For grain dislodgement removal mode, the relationship for the removal rate in scratching based on a simple fracture mechanics analysis has been established. This research provides valuable insights into the surface and subsurface integrity and material removal mechanism during high removal rate grinding of silicon carbide.     

Development of an ultrathin BD-PCD wheel-tool for in situ microgroove generation on NAK80 mold steel

This study presents the development and application of an ultrathin diamond wheel-tool that combines in situ reverse RWEDM (rotary wire electrical discharge machining) with in situ HSFSG (high-speed and fast-shallow grinding) technique for directly generating precision microgrooves onto NAK80 mold steel. The mechanism for reverse RWEDM involves the brass wire being located beneath the disk workpiece to upwardly machine it by spark erosion. The method is employed for thinning a diamond wheel-blank made of boron-doped polycrystalline composite diamond (BD-PCD). The good electrical conductivity of BD-PCD allows for an ultra-thin grinding-edge of 5-μm thickness to be produced on the wheel blank. The HSFSG technique is used to successfully grind micro-grooves in NAK80 mold steel. The method overcomes the traditional obstacles to using diamond to machine steel by having excellent metal removal rates. Experimental results prove the precision of the microgrooves generated. Nanometric grinding depth results in much less friction allowing for the cold machining conditions and preservation of diamond's sp³ bond structure. The grinding-edge has an extremely low wear rate of just 0.1 μm per 280 mm of grinding. The factors influencing formability, thermal machinability, graphitizing of diamond and the wear process of the BD-PCD wheel-tool are discussed in detail.     

Study on micro-topographical removals of diamond grain and metal bond in dry electro-contact discharge dressing of coarse diamond grinding wheel

A coarse diamond grinding wheel is able to perform smooth surface grinding with high and rigid grain protrusion, but it is very difficult to dress it. Hence, the dry electro-contact discharge (ECD) is proposed to dress #46 diamond grinding wheel for dry grinding of carbide alloy. The objective is to understand micro-topographical removals of diamond grain and metal bond for self-optimizing dressing. First, the pulse power and direct-current (DC) power were employed to perform dry ECD dressing in contrast to mechanical dressing; then the micro-topographies of diamond grains and metal bond were recognized and extracted from measured wheel surface, respectively; finally, the relationship between impulse discharge parameters and micro-topographical removals was investigated with regard to grain cutting parameters, dry grinding temperature and ground surface. It is shown that the dry ECD dressing along with spark discharge removal may enhance the dressing efficiency by about 10 times and dressing ratio by about 34 times against the mechanical dressing along with cutting removal. It averagely increases grain protrusion height by 12% and grain top angle by 23%, leading to a decrease 37% in grinding temperature and a decrease 46% in surface roughness. Compared with the DC-25V power along with arc discharges, the Pulse-25V power removes the metal bond at 0.241 mm³/min by utilizing discharge energy by 73% and diamond grain at 0.013 mm³/min through surface graphitization, respectively, leading to high and uniform grain protrusion. It is confirmed that the impulse discharge parameters are likely to control the microscopic grain protrusion topography for efficient dressing according to their relations to the micro-removal of metal bond.     

Dressing of metal-bonded superabrasive grinding wheels by means of mist-jetting electrical discharge technology

Preparation of superabrasive grinding wheel becomes one of the most important subjects on precise machining field at present. In this research, mist-jetting electrical discharge dressing (MEDD) technology was applied to dress metal-bonded superabrasive wheels. The author proposed a systematical study on the mechanism of selective removal of the bond of wheel. An experimental study has been carried out on a Die-Sinking Electrical Discharge Machine. The quality of wheels under different dressing electrical parameters was analyzed in terms of wheel profiles and wheel topographies. In addition, the performance of MEDD’ed wheel was evaluated by measuring grinding forces. Experimental results indicate favorable dressing quality can be obtained under suitable processing parameters, and MEDD is feasible for metal-bonded superabrasive grinding wheel.     

In-process evaluation of grit protrusion feature for fine diamond grinding wheel by means of electro-contact discharge dressing

This paper introduces a new in-process evaluation method for grit protrusion feature on wheel surface by monitoring discharge current trace during electro-contact discharge (ECD) dressing of metal-bonded fine diamond grinding wheel. First an impulse discharge machining experiment was carried out to investigate the correlation between metal bond removal and discharge parameters, namely discharge current I_e and discharge pulse duration τ_e. Then ECD dressing experiment for #600 diamond grinding wheel was conduced to analyses the quantitative effect of the discharge parameters (I_e and τ_e), derived from discharge current trace between wheel and dresser (electrode), on grit protrusion feature of wheel surface. The result shows that the grit protrusion feature is sensitive to the discharge parameters (I_e and τ_e) with reference to mean diamond grit size d_gm. Further, the discharge parameters (I_e and τ_e) in ECD dressing should conform to the discharge variables’ requirement of , by which the grit protrusion feature may be evaluated and the dressing process variables may be determined. Finally, the in-process evaluation method was successfully applied to ECD dressing of #1500 diamond grinding wheel for valid grinding of hard-brittle materials.     

仿鸟羽结构自润滑金刚石砂轮磨削碳化硅陶瓷实验研究

目的 减少金刚石砂轮磨削工程陶瓷材料时的砂轮磨损，改善加工表面质量。方法 以人造金刚石为磨料，青铜结合剂为黏结剂，加入一定质量分数的二硫化钼和二氧化钛纳米颗粒作为填充材料，制备出青铜结合剂自润滑金刚石砂轮。利用脉冲激光在金刚石砂轮表面烧蚀出经设计的仿鸟羽减阻几何结构，得到新型仿鸟羽结构自润滑金刚石砂轮。制备了4种不同工况砂轮，传统青铜金刚石砂轮（TGW）、纳米自润滑金刚石砂轮（NGW）、仿鸟羽结构化金刚石砂轮（FGW）、仿鸟羽结构化纳米自润滑金刚石砂轮（FNGW）以对比其磨削性能差异。开展Si C陶瓷磨削实验，研究FNGW磨削机理。从磨削力、表面质量、砂轮磨损3个方面评价FNGW磨削性能。结果 纳米颗粒的加入不会降低砂轮力学性能，砂轮表面的仿鸟羽结构激光成型烧蚀质量较高，对未烧蚀区域没有影响。与TGW相比，FGW除工件表面粗糙度值Ra与砂轮磨损有略微改善外，其他磨削性能都有明显提升。NGW磨削性能都有所提升，但提升效果不太明显。结合二者优势的FNGW，其各磨削性能都有显著提升。其中磨削力最大降低了65.1%，工件表面粗糙度值Ra最大降低了21.5%，砂轮磨损明显减少，有效提升了砂轮的使...     

Experimental investigation of surface/subsurface damage formation and material removal mechanisms in SiC grinding

The difficulty and cost involved in the abrasive machining of hard and brittle ceramics are among the major impediments to the widespread use of advanced ceramics in industries these days. It is often desired to increase the machining rate while maintaining the desired surface integrity. The success of this approach, however, relies in the understanding of mechanism of material removal on the microstructural scale and the relationship between the grinding characteristics and formation of surface/subsurface machining-induced damage. In this paper, grinding characteristics, surface integrity and material removal mechanisms of SiC ground with diamond wheel on surface grinding machine have been investigated. The surface and subsurface damages have been studied with scanning electron microscope (SEM). The effects of grinding conditions on surface/subsurface damage have been discussed. This research links the surface roughness, surface and subsurface damages to grinding parameters and provides valuable insights into the material removal mechanism and the dependence of grinding-induced damage on grinding conditions.     

在线电解修整(ELID)超精密磨削中的金刚石磨具特性研究

ELID(Electrolytic In-process Dressing)磨削技术是在电化学加工、电解磨削原理基础上发展起来的一项磨削新技术,主要用于硬脆材料超精密磨削过程中金属基结合剂超硬微细磨粒砂轮的在线修整.本文以金刚石微粉砂轮在线电解修整(ELID)磨削氮化硅陶瓷为例,着重研究了磨具特性对硬脆材料超精密磨削过程的影响.研究表明,磨具组织沿砂轮圆周的不均匀性将会导致砂轮表面钝化膜状态的不一致,这将直接影响砂轮局部参与切削的磨粒数量,影响单个磨料的实际磨削厚度.这首先将对工件表面的磨削质量,特别是对表面粗糙度产生直接影响,同时也非常不利于实现材料的高效去除.     

干磨新工艺的试验研究

磨削加工时需要非常高的能量输入,导致磨削区温度升高,因此干磨变得非常困难。介绍一种新的方法来减少热能,即在特殊条件下使用金刚石修整器来修整CBN砂轮,使砂轮表面磨粒面积减少。实验结果表明:与同样的材料磨除率下的普通砂轮磨削过程比较,该砂轮的磨削力大幅下降,没有磨削烧伤和工件表面损伤发生。     

陶瓷金刚石砂轮在YG10X顶锤磨削加工中的应用

采用自行设计的陶瓷结合剂金刚石砂轮加工硬质合金顶锤,用低浓度金刚石砂轮加工其平面,用高浓度金刚石砂轮加工其外圆,并与树脂金刚石砂轮的磨削加工进行对比。实验结果表明:同等条件下陶瓷金刚石砂轮的锋利度要高于树脂金刚石砂轮的锋利度,其加工速度更快,且磨削产生的热要远低于树脂砂轮的;平面磨削中,陶瓷金刚石砂轮通过调整工艺参数或调细金刚石粒度能够获得更好的表面粗糙度;外圆磨削中,陶瓷砂轮较树脂砂轮加工效率提升约50%,当陶瓷金刚石砂轮浓度达到200%时,砂轮性价比最高。      

金属结合剂金刚石砂轮表面微槽的激光修整技术

针对金属结合剂金刚石砂轮表面微槽修整困难的问题,采用红外纳秒激光器开展修整试验,探究激光功率、脉冲重复频率、激光烧蚀时间等因素对其材料去除的影响规律,并对U型和V型2种砂轮微槽提出梯度步进激光修整工艺。结果表明：修整后的砂轮微槽实际轮廓与设计轮廓对比,其顶部和底部实际宽度相对误差的绝对值最大为4.4%,实际深度相对误差的绝对值最大为9.6%。用修整后的砂轮V型微槽对直径为4英寸(10.16 cm)的蓝宝石晶圆边缘进行倒角,晶圆锐利的边缘被修整成规则形状,边缘轮廓对称度良好,且与激光修整后砂轮表面的微槽轮廓一致,验证了金属结合剂金刚石砂轮表面微槽激光成型修整的可行性。