THERMAL DISPLACEMENT CORRECTING METHOD FOR SCREW FEED MECHANISM

PURPOSE:To accurately correct positioning error due to thermal displacement extending over full length of a feed screw, even when a part of a feed screw is usually used and another part is occasionally used. CONSTITUTION:A feed screw 3 consisting of a ball screw and the like is supported with the brackets 5, 6 of a bed 1 through bearing 7, 8, given with prescribed pretension. A feed motor 10 provided with a position detector 9 is combined with the right end of the feed screw 3. A measuring part 11 is provided on the left end of the feed screw 3, the gap quantity (g) is detected with a gap sensor 12, and measured with a detecting apparatus 13. The thermal displacement quantities of respective points in the lengthwise direction of the feed screw 3 are computed by an NC control device based on the measured displacement quantity, a mechanical constant, and the like, and the correcting value for positioning error is decided.