Electrolytic In-process Dressing Grinding Research Articles

State control of passivating films in electrolytic in-process dressing precision grinding for silicon nitride

The functions of the passivating film, the factors influencing the thickness and compactness of the film and the control strategies of the film state in Electrolytic In-process Dressing (ELID) precision grinding were analysed. The loop current, which can characterise the film state was monitored and the experiments of the ELID grinding were conducted in the active controlling of the film state.

Modeling of Ultra-Precision ELID Grinding

The electrolytic in-process dressing (ELID) grinding is a new and an efficient process for ultra-precision finishing of hard and brittle materials. Unlike conventional grinding processes, the ELID grinding is a hybrid process that consists of a mechanical and an electrochemical process, and the performance of the ELID grinding process is influenced by the parameters of the above said processes. Therefore, it is necessary to develop a new grinding model for the ELID grinding, which can be used to avoid the cumbersome and expensive experimental trials. In this paper, the authors proposed a new grinding model for ultra-precision ELID grinding. The main focus is to develop a force model for the ultra-precision ELID grinding where the material removal is significantly lower than the conventional grinding. When the material removal rate is very low, it is very important to estimate the real contact area between the wheel and work surfaces. The developed grinding model estimates the real contact area by considering the wheel and the work surface characterization and the effect of the electrolytic reaction at the grinding wheel edge. The effects of the microstructure changes on the wheel surface by the electrochemical reaction have been implemented in the model in order to improve the efficiency of the developed model. The grinding model has been simulated and the simulated results are substantiated by the experimental findings.

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.

A Fundamental Study on Optimal Oxide Layer of Fine Diamond Wheels during ELID Grinding Process

In ELID (Electrolytic In-process Dressing) operations, the setting of starting point is quite important for reducing waste of time and for achiving high quality surface. In this study, the authors proposed a new describing mode for ELID grinding. The oxide layer formed on the wheel surface was divided to four sub-layer: porous-layer, polishing-layer, grinding-layer and interface-layer. The influence of the oxide layer on material removal rates and surface properties was investigated. It was found that, olny the oxide layer with thickness less than 24'm has capability of material removal. In ELID grinding, optimal thickness of the oxide layer is about 8~9'm. And the oxide layer with thickness of 4~9'm is suitable for grinding.

In-Process Truing of Metal-Bonded Grinding Wheels by Pulse Width Control in ELID Grinding(Nanoprecision Elid-grinding (continued))

This paper proposes an in-process truing method for metal-bonded diamond grinding wheels in electrolytic in-process dressing (ELID) grinding. In general ELID peripheral grinding, dressing voltage is equally supplied on the periphery of a grinding wheel, so that it is uniformly dressed. In contrast, in this study, an attempt has been made to supply dressing voltage in proportion to the wheel radius by the pulse width control in order to improve the roundness of the grinding wheel. For this purpose, a wheel profile monitoring system and a pulse controllable power supply were developed and the in-process truing procedure was designed. Finally, its effectiveness was verified experimentally.

Ultraprecision ELID grinding for Micro Lens Mold(Nanoprecision Elid grinding)

In this study, The ELID micro grinding method and inclined rotational grinding by three-axis motion control (XYZ axis) was carried out on a micro aspherical mold. ELID (Electrolytic In-Process Dressing) grinding method is possible to achieve ultraprecision smooth surface of hard and brittle materials. To obtain ultra smooth surface required such as micro lens, final polishing process taken long tune after conventional grinding process was necessary. ELID grinding method using an ultraprecision grinding machine tool has been found to be effective in reducing the time required for finial polishing process in this study. Results of this grinding experiments indicated that ultraprecision surface roughness and form accuracy was achieved successfully. High profile accuracy into effective diameter within ±0.1μm p-v was successfully achieved in this grinding experiment too.

A New Fabrication Method of Neutron Fresnel Lens

In order to improve the application of neutron scattering technique, a new neutron optical device, which optical system consists of an array of several ten neutron Fresnel lenses, is designed by the researcher engaging in the study of neutron optics. Neutron Fresnel lenses for this new device have the same symmetric concave form. Its center is a spherical surface and the other surfaces are conic section. MgF2 single crystal glass is selected as the material for making neutron Fresnel lens because of its high transparence. Considering the form complicity and the brittle properties of MgF2 material, the fabrication of neutron Fresnel lens is of very difficulty. Form ELID (electrolytic in-process dressing) grinding was used for grinding the neutron Fresnel lens in this first study. The optima of grinding conditions for #325, #1200 and #4000 cobalt bonding diamond abrasive wheels are obtained through a series of tests. The MgF2 material is removed at the ductile mode by using #4000 abrasive wheel. Thus, the neutron Fresnel lens fabricated has low roughness and high transparence. The transmission of an array of 50 pieces of neutron Fresnel lens is 92.5 percents to neutron beam with wavelength 5Å and 79.3 percents to 16Å.

Simulation and Analysis of Rigid/Foil Electrolytic In-Process Dressing (ELID) Systems for Grinding

The fluid flow problem in a traditional electrolytic in-process dressing (ELID) system is analyzed and solved numerically. The predicted mean velocity profiles in the dressing zone show flow patterns that are in good agreement with the mean velocity distributions for plane laminar/turbulent Couette flows observed in the experiments. The computational results reveal that insufficient electrolyte supply rate is the cause of the failure of the traditional ELID system for high-speed grinding. Results also show that to obtain effective high-speed ELID grinding, a consistent high inlet electrolyte velocity or supply rate is required. For the foil ELID system, governing equations describing the fluid flow in the dressing zone and the foil elastic deformation are formulated. Analytical solution based on unidirectional flow model for the problem is presented and effects of wheel surface speed and foil tension on the performance of the dressing system are discussed. It is shown that the foil ELID system has the potential to be effective for high-speed grinding with low electrolyte supply rates. The results will be useful to the development of new machine systems and processes for high-speed grinding.

Investigation of pre-dressing time for ELID grinding technique

The grinding wheel topography and the macroscopic wheel shape generated by truing and dressing are one of the major concerns of the manufacturers of high accuracy component parts. Decreasing the dressing time is always desirable as it may reduce the processing time and production costs. A new dressing technique—electrolytic in-process dressing (ELID)—has attracted special interest recently because eliminates the conventional dressing times while it increases the ground surface quality. The primary purpose of the ELID is the generation or regeneration on the desired topography of the grinding wheel that is necessary for assuring the quality of the finished part. Excellent smooth surfaces can be achieved with the use of extremely fine abrasives. This paper presents the results of a theoretical and experimental study of the pre-dressing time for an ELID setup applied to a CNC surface-grinding machine. The theoretical analysis of the pre-dressing time was completed based on the fundamental electrochemical laws. The model of Hong and James concerning the electric field or current density distribution around a diamond particle embedded in a metal anode during ELID was employed. In parallel, a predictive model of the pre-dressing time values was built on the basis of recorded experimental data. Good correlation of the predicted values given by the theoretical and the experimental model was found. An optimization of the pre-dressing time for the considered case was performed in order to improve the efficiency and productivity of the process.

Subsurface Properties of Ceramics for Lightweight Mirrors after ELID Grinding

In the development of large-scale astronomical telescopes, certain new ceramics such as Silicon Carbides (SiC) and glass-ceramics (Zerodur) are applied for primary mirrors. However, the surface finishing of these ceramic mirrors is very time consuming by traditional polishing processes. In this study, a highly efficient process called ELID (Electrolytic In-process Dressing) grinding was conducted to grind ceramics for lightweight mirrors (CVD-SiC, Sintered-SiC, Zerodur). The dependence of subsurface properties on grinding process parameters was investigated. The subsurface damages on the ground surfaces were observed by AFM. The results demonstrated that crack-free surface could be obtained for CVD-SiC and Zerodur using cast iron bond diamond wheel with grain size of 4µm. The total depth of cut needed was found to be between 13 and 20µm. It was difficult to eliminate the subsurface damages generated on the ground surface of Sintered SiC, even though the depth of cut was as small as 0.1µm.

525 人工骨頭用材料のELID研削による高機能表面の創製(OS11 研削・砥粒加工)

In order to apply an ELID (Electrolytic In-process Dressing) grinding as a finishing method for Co-Cr alloy used as biomaterials, we performed a detailed analysis of the ELID ground surface. The roughness of ground surfaces were measured by a contact type roughness meter and then detail observation was carried out by an Atomic Force Microscopy (AFM).The analysis of the ground surface was performed by an X-ray Photoelectron Spectroscopy (XPS). Results showed that the ELID grinding achieved the high quality surface and created a thicker oxide layer compared with the polished surface.

Nano finish grinding of brittle materials using electrolytic in-process dressing (ELID) technique

Recent developments in grinding have opened up new avenues for finishing of hard and brittle materials with nano-surface finish, high tolerance and accuracy. Grinding with superabrasive wheels is an excellent way to produce ultraprecision surface finish. However, superabrasive diamond grits need higher bonding strength while grinding, which metal-bonded grinding wheels can offer. Truing and dressing of the wheels are major problems and they tend to glaze because of wheel loading. When grinding with superabrasive wheels, wheel loading can be avoided by dressing periodically to obtain continuous grinding. Electrolytic inprocess dressing (ELID) is the most suitable process for dressing metal-bonded grinding wheels during the grinding process. Nano-surface finish can be achieved only when chip removal is done at the atomic level. Recent developments of ductile mode machining of hard and brittle materials show that plastically deformed chip removal minimizes the subsurface damage of the workpiece. When chip deformation takes place in the ductile regime, a defect-free nano-surface is possible and it completely eliminates the polishing process. ELID is one of the processes used for atomic level metal removal and nano-surface finish. However, no proper and detailed studies have been carried out to clarify the fundamental characteristics for making this process a robust one. Consequently, an attempt has been made in this study to understand the fundamental characteristics of ELID grinding and their influence on surface finish.

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.

2916 ELID 研削によるシリコンウエハの超薄厚加工

For grinding the ultra thin wafer, an ELID-grinder for substrates had developed. In this study, the authors thus attempted the mirror surface grinding of thin silicon wafer by the electrolytic in-process dressing (ELID) grinding method, which has been successfully used to obtain efficient and high quality ground surfaces of brittle materials. In the experiments, #2000 and #4000 cast bonded diamond wheels were used to investigate the ELID grinding characteristics of silicon. The results of the experiments showed that the ground surface roughness improves as the abrasive diameter becomes smaller, and a high quality-grinding surface of 7.0 nm Ra can be achieved with the #4000 wheel, and good surface flatness can be obtain.

202 Ultraprecision Fabrication of Glass Ceramic Aspherical Mirror by ELID grinding Method

Glass-ceramic aspherical mirrors used as optical elements in space astronomical observatory must be machined with very high profile accuracy and surface smoothness. Precision grinding processes are very effective in fabrication of such profiles. In particular, ELID (Electrolytic In-Process Dressing) grinding method is possible to achieve ultraprecision smooth surface of hard and brittle materials. To obtain ultra smooth surface required by astronomical observatory, final polish process which required long time after conventional grinding process was necessary. ELID grinding method using an ultraprecision grinding machine tool with nano-level hydrostatic guide will be very effective in reducing the time required for finial polishing process. In this paper, a new ELID grinding system is introduced and experimental results of fabricating glass-ceramic paraboloidal mirror are discussed.

Variations in Corrosion Resistance of Ti-Ni Alloy Tooled by ELID （Electrolytic In-Process Dressing） Grinding Methods under the Mouth Condition

Variations in Corrosion Resistance of Ti-Ni Alloy Tooled by ELID （Electrolytic In-Process Dressing） Grinding Methods under the Mouth Condition

金属系生体材料（Ｔｉ−６Ａｌ−４Ｖ合金）の腐食特性に及ぼすＥＬＩＤ研削の効果

ELID (Electrolytic In-process Dressing) grinding method was used as a surface fabrication process for metallic biomaterials (Ti-6Al-4V alloy), and ground surfaces were analyzed by a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Spectroscopy (EDX). To measure the thickness of surface oxide layer, detailed observation was also performed by a Transmission Electron Microscope (TEM). Electrochemical corrosion tests were carried out using a three electrode electrochemical cell connected to a computer driven potentiostat. The finished surface ground by the ELID grinding method showed higher corrosion resistance compared to the surface finished by polishing. This is because the ELID grinding method created a thick oxide layer. Consequently, the ELID grinding method appears to offer significant future promise for use in biomaterials and other engineering components subjected to corrosion.

A study on the grinding of glass using electrolytic in-process dressing

Grinding of brittle materials such as glass is gaining importance due to the rapid developments in the areas of machining of storage devices, microlenses, and optical communication devices. Grinding of such glasses is difficult because grinding wheels wear out easily due to the hard and brittle nature of the materials being machined. Grinding wheels with fine abrasive size are required in order to achieve ductile mode grinding. Problems such as wheel loading and glazing can be encountered while grinding with fine abrasive wheels. Electrolytic in-process dressing (ELID) is an efficient method to dress the grinding wheel while performing grinding. In this paper, a fundamental study on the mechanism of the ELID grinding technique is discussed in detail. Several sets of experiments have been performed to determine the optimal grinding conditions. From the experiments, it has been established that surface roughness could be further improved if the current duty ratio to dress the grinding wheel were increased. The force patterns and the changes in the profile of the grinding wheel during machining are also presented and discussed in detail.

High efficiency ELID grinding of garnet ferrite

Hard and brittle materials such as ferrite, optical glass and ceramics have been used in many fields and still gain increasing attention. They are difficult to machine and it is hard to obtain good surface quality. Some workpieces of large batch production have large machining allowances and the machining efficiency is low with the usual grinding method. Thus it is of great importance to research the high efficiency grinding technology of hard and brittle materials. In this paper a cast iron bond diamond wheel and ELID (electrolytic in-process dressing) grinding technology are used on a surface grinder to research the high efficiency grinding technique. ELID grinding has been used previously in precision grinding with a fine abrasive wheel. In this study, the feasibility of ELID grinding for high efficiency deep-cut grinding has been researched. Garnet ferrite (YAG) has been machined both by the new method and by using a resin bond diamond wheel. The grinding force of the cast iron bond diamond wheel with ELID technology is apparently smaller than that of the other method. Under the same conditions, it is about 2/5–3/5 of the force using the resin bond diamond wheel. The result indicates that the grinding efficiency of garnet ferrite can be highly improved and good surface quality ensured by applying ELID grinding technology and adopting a large grinding depth.

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.