Experimental study of ELID grinding based on the active control of oxide layer

The oxide layer state directly relates to the grinding efficiency and machining quality in Electrolytic In-process Dressing (ELID) grinding. In order to monitor and control the state of the oxide layer, a new high-frequency pulse power source is proposed for ELID grinding. It uses the superposition of big and small pulses to achieve periodical electrolysis and to adjust oxide layer state. Based on an analysis of current change with duty cycle, a pulse-based fuzzy control program was designed to control the state of the oxide layer within a certain range and the oxide layer grinding efficiency in different oxide layer states was studied. The results show that the new power source could maintain a stable grinding process and that the dressing current should be controlled according to the grinding wheel grain size.     

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.     

应用ELID技术进行微晶玻璃超精密磨削

由于微晶玻璃具有优良的物理、机械性能，在光学等领域得到了越来越多的应用。ELID磨削利用在线．电解的方法修整超细粒度的金刚石砂轮，可以有效地实现硬脆材料的超精密加工。本文将ELID磨削技术应用于微晶玻璃的超精密加工，通过改进ELID磨削的关键技术，包括砂轮电火花整形、电解修整电源和ELID磨削液的改进，实现了微晶玻璃的超精密磨削加工，同时通过采用原子力显微镜对不同磨削参数下的工件表面进行分析，以保证在塑性状态下对微晶玻璃进行磨削。因此提高了ELID磨削的质量。获得了Ra2．308nm的较好表面质量。     

ELID磨削试验电解参数对光学玻璃表面质量的影响研究

随着国防尖端技术的迅速发展,许多具有独特性能的新材料得到了日益广泛的应用,如光学玻璃、硬质合金.但采用传统磨削工艺加工这些材料很难得到良好的表面质量.在线电解砂轮修整(ELID)磨削技术是一项新的、高效的磨削方法,它有效实现了许多难加工材料的超精密加工和高效加工.针对光学玻璃的特性,将ELID磨削方法应用于光学玻璃的精密加工,通过试验研究ELID磨削中电解参数对加工表面的影响规律,找到了在一定条件下优化的电解参数.试验结果表明,在ELID中,工艺参数对磨削质量及磨削效率有着显著影响,优化工艺参数对ELID镜面磨削有着重要的意义.     

GCr15钢的ELID磨削性能实验研究

为了探讨GCr15钢的ELID（Electrolytic In-process Dressing）磨削性能，在基于大量实验的基础上，对GCr15钢采用ELID磨削时磨削力的变化规律进行了详细分析，并将磨削力、磨削表面粗糙度与普通磨削进行了比较。结果表明，采用铸铁结合剂CBN砂轮进行ELID磨削时磨削力几乎不随时间的变化而变化，而采用白刚玉砂轮进行磨削时的磨削力随时间的变化不断增大，在线电解修整使CBN砂轮在磨削过程中始终保持良好的磨削性能，有利于节省砂轮修整时间，提高加工效率。在ELID磨削中，采用微细砂轮进行磨削可以获得很低的表面粗糙度，实现对GCr15钢的超精密镜面磨削。     

A fundamental study on the mechanism of electrolytic in-process dressing (ELID) grinding

Demands for high quality surface finish, dimensional and form accuracy are required for optical surfaces and it is very difficult to achieve these using conventional grinding methods. Electrolytic in-process dressing (ELID) grinding is one new and efficient method that uses a metal-bonded diamond grinding wheel in order to achieve a mirror surface finish especially on hard and brittle materials. However, studies reported so for have not explained the fundamental mechanism of ELID grinding and so it has been studied here by conducting experiments to establish optimal grinding parameters to obtain better surface finish under various in-process dressing conditions. In this research the results show that the cutting forces are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of the grinding wheel; however, a smoother surface can be obtained using a high dressing current duty ratio at the cost of high tool wear. ELID grinding is efficient for feed rates of less than 400 mm/min, and surface cracks are observed when it exceeds this limit.     

A comparative study: surface characteristics of CVD-SiC ground with cast iron bond diamond wheel

Efficient precision machining of CVD-SiC (chemical vapor deposited silicon carbide) reflection mirrors in extremely low surface roughness and high form accuracy is greatly demanded by advanced industrial fields. The existing lapping methods have a great difficulty in satisfying these demands. Some researchers proposed ductile mode grinding technology, but it inevitably required a very expensive grinding machine, and its grinding process with such fine abrasive wheel was usually unstable. Dr. H. Ohmori put forward a new idea of application of ELID-grinding to ultraprecision grinding of CVD-SiC mirrors. The method had a potential to solve the above problem. In this paper, the precision grinding of CVD-SiC was performed by two kinds of methods. One is the ELID grinding; the other is the ordinary grinding with the saw-like-abrasive-stone-dressed cast iron bond diamond wheel. A comparative study of surface characteristics of ground CVD-SiC has been carried out. The following conclusions have been drawn below. (1) The surface characteristics of wheels dressed by these two methods are different. (2) The surface roughness ground by ELID grinding was only slightly better than the one produced by the ordinary grinding method. (3) The microscopic characteristics of CVD-SiC ground by these two methods differed largely. (4) ELID grinding is greatly recommendable in precision grinding of hard-brittle materials on ordinary machines of low rigidity.     

ELID grinding and tribological characteristics of TiAlN film

This paper presents the results of electrolytic in-process dressing (ELID) grinding experiments performed on TiAlN film and characterization of the tribological characteristics of the produced films. In advanced films coated by physical vapor deposition, such as CrN and TiAlN, the low surface roughness required for attaining superior tribological characteristics is difficult to attain by use of only a coating process. ELID of grinding wheels improves wheel performance, enabling the attainment of specular finishes on brittle materials, with surface roughness on the nanometer scale (4 to 6 nm). In the present study, high-quality TiAlN film surfaces were fabricated by the ELID technique, typically achieving a surface roughness of around Ra 0.0024 μm by employment of a SD#30,000 wheel. Scanning electron microscopy reveals that ELID improved the finish, as indicated by the shape of grinding marks. Chemical element analysis by an energy-dispersed x-ray diffraction system suggests that ELID grinding formed an oxide layer in the machined surface of TiAlN film. Therefore, in addition to the highly smooth surface, an oxide layer formed by ELID grinding imparts superior tribological properties to ELID-ground TiAlN film.     

氧化铝陶瓷ELID高效磨削技术的研究

陶瓷材料具有优异的机械性能，其应用越来越广泛。然而由于陶瓷的高硬度及其易碎性使其难于加工。在线电解修整磨削技术已经被应用于硬脆材料的超精密加工，由于可以实现砂轮的在线修整，尤其被广泛应用于细粒度砂轮的磨削中。本文在平面磨床上应用铸铁结合剂金刚石砂轮与ELID磨削技术进行高效磨削研究。实验结果表明，在同样的磨削条件下，采用ELID磨削时的磨削力约为使用树脂结合剂砂轮磨削力的2／5～3／5。实验结果说明采用ELID磨削技术加工效率可以得到极大提高。而且，在线电解修整作用可以保持砂轮的锋锐性，有利于保持硬脆材料高效磨削的连续性。     

基于ELID磨削WC-Co硬质合金表面机械研抛研究

本文采用ELID磨削和机械研磨抛光复合技术,对WC-Co硬质合金表面进行了超精密加工实验研究。首先采用ELID磨削对WC-Co硬质合金表面进行预加工,获得表面粗糙度Ra18 nm的精密加工表面。在此基础上对其进行机械研磨抛光加工,研抛盘转速设定为150～200 r/min,研抛压力控制在0.2～0.5 N/cm2范围;机械研抛时,首先采用含W1金刚石磨粒的研抛液,对ELID磨削后的表面进行加工100min左右,以达到快速去除的目的。再用含W0.5金刚石磨粒的研抛液,进行机械研抛约100 min,最后获得Ra4 nm的超精密表面。同时,针对机械研磨抛光过程,本文深入研究了磨料种类、粒度、抛光液溶剂、研抛压力、研抛加工时间等因素对加工表面粗糙度的影响。     

ELID grinding of silicon wafers: A literature review

Silicon wafers are the most widely used substrates for fabricating integrated circuits. There have been continuous demands for higher quality silicon wafers with lower prices, and it becomes more and more difficult to meet these demands using current manufacturing processes. In recent years, research has been done on electrolytic in-process dressing (ELID) grinding of silicon wafers to explore its potential to become a viable manufacturing process. This paper reviews the literature on ELID grinding, covering its set-ups, wheel dressing mechanism, and experimental results. It also discusses the technical barriers that have to be overcome before ELID grinding can be used in manufacturing.     

W-Mo合金精密镜面加工工艺的实验研究

为了研究W-Mo合金材料精密加工的新途径,采用在线电解修整(ELID)精密磨削和超精密研抛技术,对其进行了精密镜面加工实验,分析了此材料超精密镜面表面的形成机理。通过ELID磨削加工得到了表面粗糙度Ra0.020μm加工表面,再以研抛压力为0.1~0.3 N/cm2,转速为60~100 r/min等优化研抛参数进行研抛加工,获得了表面粗糙度为Ra0.012μm精密镜面加工表面。实验表明:ELID精密磨削加工是保证工件表面质量的基础,超精密机械研抛时研抛压力及转速等参数对工件表面质量起主要影响作用。     

超声振动磨削放电复合加工SiCp／Al试验研究

针对SiCp／Al的加工,提出一种超声振动磨削放电复合加工的方法．从加工效率、加工稳定性及表面质量等方面与电火花加工进行了对比试验研究。分析了两种加工方法的脉冲宽度和峰值电流对加工速度和表面粗糙度的影响,结果表明：电火花加工的表面粗糙度平均值为尺04．5μm,超声振动磨削放电复合加工的表面粗糙度平均值为Ra2μm：超声振动磨削放电复合加工的稳定性比电火花加工好,但加工速度较低。通过扫描电镜对两种加工方法下零件表面形貌和重熔层进行了观测,对试件表面进行了X射线衍射分析,表明采用超声振动磨削放电复合加工SiCp／Al复合材料可获得较好的表面质量。     

Depth-of-cut errors in ELID surface grinding of zirconia-based ceramics

Based on the analysis of a surface grinding system and the material removal mechanism, a mathematic model has been proposed to predict the accumulated error between the total set depth-of-cut (DoC) and the total actual depth-of-cut (ADoC) in multi-pass surface grinding of zirconia-based ceramic materials. Design of Experiments (DoE) approach has been implemented to carry out experiments. The influence of the set DoC of each grinding pass, the total set DoC, and the grinding wheel velocity on the accumulated errors in ADoC has been investigated in detail in surface grinding of zirconia-based ceramics both with electrolysis in-process dressing (ELID) and without ELID. It has been observed that the accumulated DoC errors increase faster in the first few passes and gradually reach a saturation after a certain total DoCs (about 8–10 grinding passes) and a higher step DoC leads to a faster (fewer passes) saturation of the accumulated DoC errors. Compared to grinding without ELID, it has been found that ELID-grinding is characterized with better process stability and ELID offers positive effects on material removal rate (MRR), especially in case of removing large volume of material with the same grinding parameters.     

以工件材料作为修整电极的球面ELID精密磨削试验研究

针对小球面硬质合金精密磨削的技术难题,尝试对硬质合金做ELID(Electrolytic In-process Dressing)成形范成法凹球面磨削试验。因为被加工凹球面直径小,受空间限制无法解决修整电极的安装问题,又由于硬质合金工件自身导电性良好,因此采用以工件做电极的ELID磨削试验方案。考虑到磨削过程中的火花放电现象对磨削表面质量的负面影响,设计"间歇电解修锐ELID磨削"(简称ELID-Ⅱ)和"连续电解修锐ELID磨削"(简称ELID-Ⅲ)两种方案进行试验。初步试验结果为:"ELID-Ⅱ"磨削后表面粗糙度值为Ra0.12μm和球面度误差6.99μm,"ELID-Ⅲ"获得表面粗糙度值为Ra0.53μm和球面度误差57.76μm,"ELID-Ⅱ"优于"ELID-Ⅲ"。     

精密ELID镜面磨削用新磨削液的研制

本文以已有的HDMY-10型ELID磨削液的配方为参照，根据ELID磨削的特点和要求，通过减少或增加无机盐、添加剂等成分的比例，找出了ELID磨削中生成氧化膜性能与磨削液成分的关系，研制出新型的性能更好的ELID磨削液。     

采用CBN砂轮磨削气缸体Ni-SiC复合镀层

与离子溅射、火焰溅射、CVD等方法相比较, 采用电沉积方法形成的复合镀层有着非常优越的性能,但同时复合镀层的精密加工亦成为制约其性能发挥的关键.某小型航空发动机气缸体中由于有Ni-SiC复合镀层,其内孔磨削的难加工是制约该型号发动机性能的关键工艺.针对该缸体的特殊结构及镀层特点,文中采用合理的装夹方式及磨削工艺参数,在精密内圆磨床上采用陶瓷结合剂CBN砂轮实现了对Ni-SiC复合镀层内孔的磨削.实践证明,该工艺方法解决了Ni-SiC弥散复合镀层的精密加工难题,提高了加工效率,改善了表面尺寸形状精度和表面粗糙度.     

氮化硅陶瓷ELID磨削预修锐与氧化膜成膜的影响因素

针对氮化硅陶瓷回转曲面零件高效低损伤的加工要求,设计适用于回转面加工的在线电解修整（ELID）磨削实验装置,在数控坐标磨床上进行预修锐实验。基于平行电极电解池模型,建立预修锐时间与氧化膜成膜厚度的关系模型,分析占空比和极间间隙对成膜效果的影响规律。结果表明:工艺参数对预修锐时间的影响程度依次为占空比>电解液流量>砂轮转速>脉冲频率。采用田口方法获得最优工艺参数组合为占空比0.75,脉冲频率50kHz,砂轮转速9 000r/min,电解液流量1.0 L/min。      

Surface finishing of Ni–Cr–B–Si composite coatings by precision grinding

A Ni–Cr–B–Si/10vol%WC coating material has been precision ground to an optical quality surface finish (<10 nm R_a) using a combination of a very stiff precision machine tool, Tetraform “C”, 76 μm CBN grinding wheels and electrolytic in-process dressing (ELID) assisted grinding. When grinding without ELID, surface finish has been shown to be limited by damage to primary and secondary carbides. This damage may be in the form of carbide pull-out or localised fracture and removal of the larger primary WC particulate. ELID assisted grinding helps maintain CBN grit protrusion and sharpness and thus promotes efficient cutting during grinding, minimising pull-out and localised damage to the harder phases within the coating microstructure. ELID therefore improves both the overall surface finish and surface integrity of the workpiece.     

ELID precision grinding of large special Schmidt plate for fibre multi-object spectrograph for 8.2 m Subaru telescope

To explore various scientific frontiers from nearby substellar objects to large scale structures of the high redshift universe, a Fibre Multi-Object Spectrograph (FMOS) is being developed as the second generation near-infrared measuring instrument for the prime focus of 8.2 m Subaru telescope in Hawaii, which employs a large special Schmidt plate element. The Schmidt plate consists of a large non-axisymmetric aspherical concave plate and a convex plate. This paper introduces its manufacturing process, focusing on its non-axisymmetric aspherical surface machining by utilizing synthetically ELID grinding and arc-enveloped grinding method. A new grinding system capable of fabricating large optical elements was developed with 10 nm resolution. In this ELID arc-enveloped grinding system, a Cast Iron Fibre Bonded (CIFB) diamond wheel was 3D controlled to scan the workpiece to generate required surface. Grinding characteristics such as attainable form accuracy, surface roughness were investigated. Furthermore, some measures to improve form accuracy were discussed and verified.