Hiroshi Kasuga

Mirror surface grinding of sapphire by coarse grain size diamond wheels

This paper discusses the grinding of sapphire for mirror surfaces by coarse grain size diamond wheels. Sapphire is a hard-to-machine material because it has excellent mechanical properties and indentation hardness. Since it is effective for hard materials to use metal-bonded diamond wheels, the authors had two experiments to investigate mirror surface grinding by coarse grain size diamond wheels. The 1st experiment was investigating appropriate grinding conditions, and the 2nd experiment was investigating protrusion height of abrasive grains. Although the conventional methods could not acquire mirror surface, the results of the experiments show that mirror surface (Ra: 5 nm <) were obtained by the #270 and #325 mesh size wheels. These results indicate the possibility of decreasing grinding processes by coarse grain size diamond wheels.

Terahertz 3D imaging with a CW source and phase-shifting interferometry

We will present two kinds of terahertz (THz) 3D imaging performed with a continuous-wave (CW) source and phase-shifting interferometry. The first one is THz computed tomography (CT) by using phase information instead of intensity information. This minimized the effect of change in the signal strength due to diffraction and artifacts especially emerged around the edge of boundary between different materials. The second one is for the depth imaging of the surface of reflecting materials. By using a simple Michelson’s interferometer, we achieved the depth resolution of 1.1 μm, corresponding to 1/440 of the used wavelength (480 μm).

Efficient and smooth grinding characteristics of monocrystalline 4H-SiC wafer

Semiconductors have a broad range of uses. In particular, semiconductors used for power conversion are generically called “power devices.” Silicon carbide (SiC) power devices have been gaining attention as next-generation semiconductors because they have excellent electrical characteristics compared to silicon power devices. However, SiC is difficult to grind efficiently because of its hard and brittle characteristic. In this study, the authors used some effective grinding methods and investigated efficient grinding conditions. As a result of their experiments, the average removal volume was 80.0% for 40μm of grinding with a 1200 mesh-size wheel.

Influence of Grinding Wheel Dressing on the Roughness of Final Surface and Cutting Force during GGG60 Grinding

Dressing of grinding wheel is important value, which can influence final surface. Therefore, it is necessary to address this issue some attention. Dressing is used for sharpening of clogged and blunted grinding wheel and adjustement of their geometric shape. The article deals with one of the experiments that are carried out in this area at FPTM JEPU in Ústí nad Labem. Experiments refer specifically to impact assessment of dressing size on the final selected values of surface integrity. Within the article, the assessment covered the surface roughness Ra, Rz and Rt. At the same time were also scanned using a dynamometer Kistler components of the cutting forces and even here it was possible to observe the influence of the dressing size of the grinding wheel on these values.

Comparison of Roughness and Profile between ELID and Ground Surfaces

This paper deals with surface roughness and surface profile in high precision methods of materials finishing. One of them is ELID process and the second method is grinding. There is surface profile and roughness compared of the three materials samples – carbide steel and two aluminium alloys. In the paper are shown results of surface measurement between ELID and ground surface. Both methods are very precision in the focus on surface roughness – measured units in nano scale. Paper shows possibilities in finishing methods for production, automotive, aerospace, medicine and cosmic industry.

Electrolytic in-process dressing grinding of sapphire with nanodiamond composite wheel

In this paper, nanodiamond (ND) was applied to a processing additives used in the manufacture to a wheel for grinding sapphire. Nanodiamond was produced by the detonation of trinitrotoluene explosives technique, and the tribological characteristics of ND solution were investigated. Sapphire was a difficult material to process with high quality, precision and efficiency. With the aim of reducing friction and friction heat between the wheel and sapphire surfaces, metal resin bonded diamond wheels (#2000, average grain size: 8 µm) containing ND with 0.2, 1.0, and 2.0 vol.% were produced. Appropriate machining parameters were selected for electrolytic in-process dressing (ELID)-grinding process (Ohmori and Nakagawa, 1990), and the grinding behaviour of sapphire was evaluated. In summary, an extremely smooth surface of sapphire wafer was fabricated by using the #2000 metal resin bonded diamond wheel containing 2.0 volume percent ND and a rotary in-feed grinder with ELID.

Surface Characteristics of Efficient-Ground Alumina and Zirconia Ceramics for Dental Applications

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.

Efficient Super-Smooth Finishing Characteristics of SiC Materials through the Use of Fine-Grinding

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 for their hard and brittle features. The authors have been investigating optimized conditions on their finishing by fine-grinding with the unique grinding process called ELID (electrolytic in-process dressing). When grinding conditions are changed to fine grinding from coarse grinding, each material has a transition phenomenon; from brittle to ductile removal. ELID 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.