Akihiko Nemoto

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.

Fabrication of High-quality Surfaces on Precise Lens Mold Materials by a new ELID Grinding Wheel

In this study, we have performed efficient and high-precision grinding of cemented carbide alloys with a newly developed grinding wheel, and investigated the ground surface characteristics in detail. The processing results showed that final finishing using the Chromium bonding #8000 wheel produced an extremely smooth ground surface roughness Ra of 4 nm. And, a very interesting finding is that use of Chromium as a bonding material further promoted the diffusion of oxygen to the surface of a workpiece.

ELID Grinding with a Tape Type Electrode

To realize efficient cleaning of an ELID electrode surface, a tape type aluminum foil electrode was proposed. The advantages were investigated. Experimental results show that the tape type foil electrode has the same initial electrolytic dressing characteristics and ELID machining characteristics as normally used metal electrodes. It was also found that the tape type electrode can be used stably in a long grinding process without problems such as peeling and melting seen. These results confirm that the tape type aluminum foil electrode can be applied to ELID grinding.

Friction and Wear Properties of an ELID-Grinding Wheel based on CCD Microscope Observation

The friction and wear properties of an ELID-grinding wheel with an oxide layer were investigated by using a CCD microscope tribosystem under dry and lubricated conditions. When the #400 diamond wheel is used as a disk specimen, the friction coefficient is 0.23-0.58 under dry conditions, and 0.11-0.38 under lubricated conditions. When the #4000 diamond wheel is used, the friction coefficient is 0.16-0.76 under dry conditions, and 0.15-0.38 under lubricated conditions. The specific wear rate (ws) of the #400 or #4000 diamond wheel with an oxide layer has a higher value than that of a cast iron bond wheel under lubricated conditions, when the contact pressure is more than 0.6 MPa. Furthermore, the ws of the #400 or # 4000 diamond wheel with an oxide layer under lubricated conditions has comparatively higher value than that of the #400 or #4000 diamond wheel under dry conditions. If the grain size is large, it is effective to decrease the friction coefficient in order to increase the cutting ability of the diamond grain.

Ultraprecision ELID-Grinding of Aspheric WC Lens Mold for Plastic Injection Molding

To cope with increasing demands on ultraprecision profiling and finishing of aspheric lens molds, we have implemented an ultra/ nanoprecision aspheric grinding system to be mounted with an ELID- capability and on-line feedback capability of profile accuracy. A WC mold has successfully ground and finished to be with several nanometric surface smoothness and with ultraprecise profile accuracy by just grinding process with ELID mechanism. Some specific conditions have been investigated to achieve better accuracy and quality on molds. This paper presentation introduce those R&D activities and also discuss on the latest achievements on this topics, with showing injected aspheric lenses by the molds.