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A new PCD material named EC-PCD (Electrically conductive polycrystalline composite diamond), which consists of electrically conductive diamond grits, has recently been developed. This paper deals with an investigation of a complex grinding assisted with electrical discharge machining (EDM) to realize high efficiency, low and stable grinding force and low wheel wear for the new EC-PCD. The effect of complex grinding assisted with EDM is compared experimentally with the standard PCD (S-PCD). The result shows that, in the complex grinding, lower and more stable grinding force is realized thanks to the material removal action in EDM and that lower wheel wear and better surface finish are attained, just when the EC-PCD is selected as a workpiece.

Electrically conductive polycrystalline composite diamond (EC-PCD), which consists of electrically conductive diamond grits, has recently been developed for the purpose of providing the material with both excellent tool property and good machinability. This paper deals with an investigation of machinability of EC-PCD by EDM with a copper (Cu) electrode. As a result, it was found that the EDM speed (Material removal rate) for EC-PCD was higher than that of the standard PCD. Although the surface roughness of the standard PCD was 13µm Rzjis at set current ip=3A, the surface roughness of the EC-PCD was 5µm Rzjis at the same current condition. Furthermore, it was observed that the EC diamond particle in EC-PCD was machined by single discharge EDM. Moreover, it was confirmed that EC-PCD was able to be applied a fine discharge profiling or a making fine holes using a rotating electrode.

The authors have been studying the effect of cellulosic nano-fiber (CeNF) with the diameter of less than 30 nm and the length of a few micrometers on the conductivity of the conductive polymer composites (PAS/PEs/CeNF) prepared from poly(aniline sulfonic acid) (PAS), a water dispersible polyester (PEs) and CeNF and confirmed that CeNF was effective for the enhancement of their conductivity, and that the conductivity enhancement was attributable to the strong adsorbing ability of CeNF to PAS molecules. Thiner CeNF has so larger surface area that it is expected to adsorb more PAS molecules on its surface, which possibly lead to further conductivity enhancement of the composites.The authors prepared thinner CeNF with the size of 16 nm by the use of ultrasonic dispersing machine. It was clarified that the thinner CeNF had a higher adsorbing ability to PAS molecules and a larger effect on the conductivity enhancement of PAS/PEs/CeNF composites.