Patent ID: 6821064
Filing Date: 2004-11-23
Classification: B23Q,G05B,Y10T

Abstract:
In a machine tool controlled by a numerical control unit comprising:a column; a spindle head vertically movable while being guided by a guide on the column; a movable member carried by the spindle head so as to be horizontally movable while being guided by a guide on the spindle head; a pair of ball screw mechanism for driving vertical feed motion of the spindle head, including first ball screw feed mechanisms disposed on the front side of the movable member and second ball screw feed mechanisms disposed on the rear side of the movable member; first servomotor for driving the first ball screw feed mechanism; second servomotor for driving the second ball screw feed mechanism; a compensator for compensating a vertical deviation of the movable member resulting from the fluctuation of the center of gravity of the spindle head caused by the feed motion of the movable member, said compensator comprising: control means for controlling the first and second servomotors on the basis of spindle head feed instructions provided from the numerical control unit; correction data storage means for storing correction data determining the relationship of a feed distance of the movable member to a compensation value for correcting a vertical deviation of the movable member; and correction means for being introduced a movable member feed instruction provided from the numerical control unit, and for reading out the compensation value corresponding to the feed distance of the movable member from the correction data storage means, to correct the spindle head feed instruction by adding or subtracting the compensation value to or from the spindle head feed instruction.