Papers by Author: T. Mishima

Abstract: Silicon carbide (SiC) materials have increasingly been needed in the wide range of industries, such as for structural components, automobile parts, space telescope, X-ray mirror, and next-generation semiconductors. However, SiC materials have difficulties in super-smooth finishing because of their hard and brittle characteristics. The authors have been investigating appropriate conditions on their finishing by fine-grinding with the unique grinding process called ELID (Electrolytic In-process Dressing) grinding method. The ELID grinding method has a stable grinding ability, so very detailed characteristics of their material-remove mechanisms were to be investigated. Surface analysis of each material has been discussed through the ELID, and this study proposes good finishing conditions for SiC. In this paper, the advantages of the applied fine-grinding are shown, and unique features on grinding characteristics of SiC through various grinding experimental parameters are described.

Abstract: Progress of new dental materials such as biocompatible metal, ceramics is being accelerated because of aging society and sophistication of medical treatment. In addition, the demand for dental implant treatment is increasing. Currently, dental implant crowns (superstructures) are formed by cutting semi-sintered ceramics and then sintering the ceramics at a high temperature. So, there is some concern that to maintain the form accuracy of the workpiece is difficult. Meanwhile, it is usually difficult to machine sintered ceramics with high precision and high efficiency. In this paper, we tried to apply grinding with metal bonded superabrasive wheels, and investigated the grinding and surface characteristics of an alumina and zirconia ceramics for dental implant superstructure due to lack of such data. As a result of experiments, sintered dental ceramics can be ground with high precision and Fe, it has harmful effect to human body, was not detected in sintered dental ceramics.

Abstract: A non-contact on-machine measurement system has been developed since various precise machines are getting lighter and smaller; therefore, processing with nano-precision is demanded recently. This system makes possible to measure with high precision without any damages and it is unnecessary for workpieces to attach or detach from a machine tool. Moreover, this system achieves on-machine form error compensation with high precision. On the other hand, the details of the system performances are still unknown. This study focuses on evaluating the performances by the comparison of the results that measured by this system and an existing measurement instrument under various conditions. As a result, this system shows an equivalent capability of measurement with high precision as the existing measurement instrument.

Abstract: We have been developing an intellectual manufacturing process applying IT (V-Cam system fabrication processes) based on Volume-CAD (VCAD) system which can express internal information of materials. This paper introduces the ultra-precision grinding, ray tracing (optical path) simulation software ‘V-Opt’ and the measurement of actual optical functions in the development of optical element taking gradient refractive index (GRIN) lens with functionally graded material properties as a model. In finish ground GRIN lens using SD#8000 wheel, the P-V (Peek to Value) of 27.07 nm, surface roughness (Ra) of 1.83 nm is obtained. ‘V-Opt’ developed for GRIN lens have two main functions; one is the visualizations of ray tracing and the other is the evaluation of spot diagram and focal length.