Abstract
Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because SiC has high stiffness, high thermal conductivity, low thermal expansion and low density. Therefore, we developed the ultra lightweight mirror by ELID grinding method which can obtain the surfaces of very hard materials efficiently. If a mirror becomes large, shape of the mirror becomes complicated, and thickness of the mirror surface and a lib part becomes thin for lightweight. Accordingly, it is thought that surface roughness of the mirror deteriorates by influence of vibration. And then, to improve the precision of the surface roughness, we did the ELID grinding by cross cut that the axis of rotation and a progress direction of a grinding wheel were vertical.
