PURPOSE: To improve machining precision and production efficiency for an object to be machined by forming a swivel plate into a box provided with a rib structure in its inside.
CONSTITUTION: A hydrostatic bearing is formed of a swivel center shaft 129 and a swivel center bearing 141, and in a hydrostatic pad arranged on the back face of a swivel base plate 110, the swivel base plate 110 is hydrostatically supported on a traverse table 105 by means of fluid supplied from a hole having a throttle. Under this condition, a motor 164 is driven, so that the swivel plate 110 is smoothly moved around the center of rotation. In this process, a swivel box 107 integrated with the swivel base plate 110 is formed into a box shape, whose inside is formed into a honeycomb structure, so that its load is lowered despite its high rigidity.
TSUKAMOTO SHIGEMI
YAMASHITA YASUHIRO
