Kazutoshi Katahira

Investigation on color-finishing process conditions for titanium alloy applying a new electrical grinding process

Abstract Titanium alloy is usually colored by coating or painting after finishing. Beyond that, however, if a stable oxide film can be successfully and efficiently generated on the surface at the time of grinding and polishing as part of surface processing, the surface properties of the processed workpiece will be greatly improved. This will also streamline surface treatment and allow for significant savings in energy and procedures. This study proposes an electrochemical processing system that organizes the thickness and structure of an oxide film generated on the processed surface by applying a direct current of extremely short pulses to the workpiece being ground. The authors focused specifically on the color of the oxide film generated on the processed surface as a result of optical interference, and studied closely the mechanism and control of this color finishing process conditions.

Force Characteristics and Deformation Behaviors of Sintered SiC during an ELID Grinding Process

Sintered SiC is one of the most promising materials for far i nfra-red and sub-millimeter telescopes. For science research, the telescope needs high initi al accuracy and in-orbit thermal stability. It is well known that SiC ceramics are very hard a n brittle. Generally, it is difficult to imagine that deformation can occur in SiC ceramics during the gr inding process. However, especially for SiC lightweight mirrors with a rib-structure, deformation of the profile caused by grinding force cannot be neglected, because it results in form e rrors. In this study, the force characteristics of sintered SiC were investigated by grinding a speci ally designed sintered SiC work. The deformation behaviors of the SiC work during the grinding process w re also investigated by ELID grinding experiments and a FEM simulation method. This paper pr esents the experimental procedure and the results of the investigation. Introduction Interest in sintered SiC has increased significantly in re cent years due to its unique physical and mechanical properties. Sintered SiC has been realized to be one of m ost promising material for far infra-red and sub-millimeter telescope [1] [2]. The advantages of sintered SiC over other materials include high hardness and stiffness, light weight, high thermal conduc tivity, insensitive to radiation and to ambient aggression, no ageing. Despite these advantages, the use of sint red SiC has not increased rapidly due in part to the high cost of machining this mate rial. The electrolytic in-process dressing (ELID) of grinding wheels attains specular finishs on s uch brittle materials, with high efficiency and surface roughness on the nanometer scale. Hence, it can s gnificantly reduce the time of post-polishing process required and reduce machining cost. On the other hand, SiC lightweight mirrors are usually design d as regular polygon rib-structures in the rear face for reducing weight. Both the optical face and t he rib of the mirror are so thin that deformation of the profile caused by grinding force cannot be neglec t d. To achieve higher profile accuracy, compensation considering the profile deformation is therefo r necessary during the finishing process of the lightweight mirrors. In this study, the f orce characteristics of sintered SiC were investigated by grinding a specially designed sintered SiC workpiece. The deformation behaviors of the SiC work during grinding processes were also invest igat d by ELID grinding experiment and FEM simulation method. Experimental System Fig.1 shows the schematic of the measuring system of grinding force. An ultra-precision grinding machine was used in this experiment. The machine has three linear axes, which can be controlled at a feeding resolution of 10nmunder full closed feedback. 3-axes double hydrost atic guideway are used for sliding machine, and hydrostatic bearing is used for the g rinding wheel spindle. The maximum workpiece size is 1200mm ×500mm along the X and Y axes. The X-axis can be driven at Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 65-70 doi:10.4028/www.scientific.net/KEM.238-239.65

Surface finishing for biomaterials: Application of the ELID grinding method

Conventional biomaterials, such as titanium alloys, require enhanced chemical stability and wear resistance, which are dependent on the quality of the surficial oxide layer. However, it is very difficult to produce a sufficiently homogenous oxide layer by polishing using isolation abrasive alone. In our previous study, we proposed a new electrical grinding method (ELID grinding). The process improves oxide formation on the finished surface, resulting in finished surfaces with very thick and potentially stable oxide layers. In this study, to ensure the fabrication of surface with desirable characteristics for biomaterials, three types of specimens, which were processed with different surface finishing methods were prepared. Processed surfaces were analyzed by using an Energy Dispersive X-ray analyzer (EDX). To measure the thickness of surface oxide layers, detailed observation were performed by using a Transmission Electron Microscope (TEM). Although the ELID ground surface shows a higher value of surface ...

An Ultraprecision On-Machine Measurement System

Ultraprecision optical components require ultra-fine smooth surface quality of sub-nanometer or sub-angstrom in Ra. To satisfy these requirements, ultraprecision on-machine measurement system is very important, by which the profile measurement and evaluation is conducted on the machine. The form accuracy is improved by compensating machining when the form accuracy is not enough. Ultraprecision on-machine measurement systems were developed for measurement with high-accuracy and high-efficiency. It was confirmed that the on-machine measurement with AFM was possible for surface roughness or complex form for local areas. In addition, a laser probe unit with a maximum resolution of 1nm, a measuring range of 10mm, a repeatability of 5.6nm and a maximum measurable angle of 60 degrees was developed. The possibility of the non-contact on-machine form measurement was confirmed for global form accuracy control.

Ultraprecision Fabrication of Glass Ceramic Aspherical Mirrors by ELID-Grinding with a Nano-Level Positioning Hydrostatic Drive System

Glass and ceramic aspherical mirrors used as optical element s in a space astronomical observatory must be machined with very high profile accuracy and surfa ce smoothness. Precision grinding processes are very effective in fabrication of su ch profiles. In particular, with the ELID (Electrolytic In-Process Dressing) grinding method, it is possibl e to achieve ultraprecise and smooth surfaces of hard and brittle materials. To obtain the ultra smooth s urfaces, a final polishing process which requires a long processing time after the conventional grindi ng process is necessary. The ELID grinding method using an ultraprecision grinding machine tool with a nano-level hydrostatic guide will be very effective in reducing the time required for the finial polishing process. In this paper, a new ELID grinding system is introduced and the experimenta l r sults of fabricating a glass-ceramic paraboloidal mirror are presented and discussed. The profil accuracy of the fabricated glass-ceramic mirror was found within 0.54 m P-V.

Diamond cutting of a large off-axis Fresnel lens Mold

The oxygen-free copper (OFC) is often used for the substrate material of the molds for the hot hydraulic press, the injection, and the light guide plate. The diamond cutting is usually used for the high precision finish process of the nonferrous metals. In this article, an OFC mold, which is used for testing the hot hydraulic press process of the large segmental double-side polymethyl methacrylate (PMMA) Fresnel lens, was designed. The rotary radius of this mold is about 1000mm and the mold must be fabricated to the high form accuracy and the low surface roughness. According to the conventional machining method, a rotary table with the radius larger than 1000mm is necessary for fabricating this mold. However, this mold is justly used for the first test of the hot hydraulic press of the large segmental double-side PMMA Fresnel lens. Thus, the fabrication of this mold should be carried out at the lower cost using the holding machine tool. In order to cut this mold on an ultraprecision air hydrostatic bearin...

Estimation of Tribological Characteristics of Electrolyzed Oxide Layers on ELID-Grinding Wheel Surfaces

The purpose of this work is to investigate tribological characteristics of electrolyzed oxide layers on ELID-grinding wheel surfaces under dry and lubricated conditions. A pin on disk type wear apparatus is used with reciprocating lower disk specimen. Two kinds of carbon bond materials CR and CRB, and cast iron bonded materials SD are used for the disk specimen. The normal load is changed from 0.49 N to 4.9 N. It was found that when two kinds of carbon resin bonded materials are used for disk specimen, friction coefficient of electrolyzed layers has a higher value than that of without electrolyzed layer. Specific wear rate of CR with electrolyzed layer is from 2 to 11 times of the one without electrolyzed layer. Specific wear rate of CRB with electrolyzed layer is from 10 to 128 times of the one without electrolyzed layer. Specific wear rate of SD with electrolyzed layer is from 45 to 461 times of the one without electrolyzed layer.

ELID Grinding Characteristics and Surface Analysis for Micro Fabrication of Advanced Ceramics

The present paper describes the highly efficient and precise ELID grinding method and presents a discussion on the ELID grinding process and the grinding characteristics of several kinds of ceramic materials. The following conclusions are obtained; (1) Good ground surface roughness and accuracy are achieved using the #4000 metal-bonded grinding wheel in through-feed centerless grinding for ZrO2 optical fiber ferrules. (2) Efficient and precise grinding of spherical lens molds with cup wheels using the ELID CG-grinding process was proposed and tested in the present study. (3) The ELID grinding method can be used to fabricate machined surfaces exhibiting desirable characteristics for hard AlN ceramics. The ELID ground AlN demonstrated a surface hardness and sliding characteristics that were superior to those of the polished series. These advantages may be attributable to the diffusion phenomenon of the oxygen element produced by the ELID grinding.

Control of surface modified layer on metallic biomaterials by an advanced ELID grinding system (EG-X)

The biocompatibility of titanium implants with different surface properties is investigated. We prepared three types of specimens, one ground by the newly developed ELID grinding system, another ground by conventional ELID grinding, and the other polished by SiO2 powder. These surfaces were characterized and, the number of cell and cytotoxicity in in-vitro were measured. Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscope (TEM) revealed that the modified ELID system can create a significantly thick oxide layer and a diffused oxide layer, and also can control the thickness of a modified layer. The results of cell number and cytotoxicity showed that the sample ground by the modified system had the highest biocompatibility. This may have been caused by improvement of chemical properties due to a surface modified layer. The above results suggest that this newly developed ELID grinding system can create the desirable surface properties. Consequently, this system appears to offer significant future promise for use in biomaterials and other engineering components.

Improvement of Corrosion Resistance and Mechanical Properties of the Biomaterial Ti-6AL-4V Alloy by ELID Grinding

Abstract. To clarify the effects of the ELID (Electrolytic In-process Dressing) grinding on surface characteristics of the biomaterial Ti-6Al-4V alloy, electrochemical corrosion tests were carried out using a three-electrode electrochemical cell connected to a computer driven potentiostat. The processed surfaces were analyzed by the X-ray Photoelectron Spectroscopy (XPS). The surface hardness of the samples was measured by a Nano Hardness Tester (NHT). The surface finished by the ELID grinding method showed higher corrosion resistance, compared to the surface finished by polishing. This is due to the influence of the oxidized layer on the surface and also due to the diffusion of oxygen. The diffused oxygen accelerates the regeneration of the oxide layer broken by the raised potential and prevents the dissolution of metal ions. Surface hardness was increased by the ELID grinding. This is because of the existence of the carbon diffused layer beneath the surface.