| 摘要 |
PURPOSE:To obtain a machine tool capable of preventing the collapse or bend of a column due to thermal stress and having little thermal displacement by arranging a plurality of feed screw shafts for moving a spindle head at nearly symmetrical positions in relation to the centroid axis of a column cross section. CONSTITUTION:A column 2 is slidably supported on a column bed 1 through a guide way 3 by means of a feed screw shaft 10. A pair of feed screw shafts 7 for moving a spindle head are rotatably supported on the column 2 by bearings 14. The screw shafts 7 are arranged at nearly symmetrical positions in relation to the centroid axis R located at the center of the horizontal cross section of the column 2. Gears 15 are fixed to the screw shafts 7 and are rotated in the same direction at the same speed through a gear 16. The nuts 17 of the spindle head 4 are coupled in the middle of the screw shafts 7 and are moved up and down. Even if a temperature difference occurs between the screw shafts 7 and the column 2, no eccentric load is applied and the column dose not collapse in the X direction and Z direction. |
