Mori Seiki Co., Ltd.

Masaaki Yokoyama

Munetaka Wakizaka

Hiroshi Mizuguchi

Kazutada Hashimoto

Mikio Iwakiri

A method and apparatus by which accurate correction values for thermal displacement is calculated even when the rotation of the main spindle is restarted after interruption. The apparatus has means for measuring the temperature near the main spindle means for estimating the thermal displacement of the main spindle on the basis of the measured temperature and a predetermined thermal displacement calculation expression, means for calculating the correction value, and means which estimates the displacement delay in re-rotation caused by the interruption of the rotation of the main spindle and calculates an adjusting displacement on the basis of the estimated displacement delay. The correction value calculating means calculates a correction value on the basis of the thermal displacement estimated by the thermal displacement estimating means alone when the main spindle is started up and rotated.

Method and apparatus for calculating correction value for thermal displacement in machine tool

The present invention provides a numerical control apparatus for a machine tool, which corrects an axial displacement of a main spindle caused due to a change in preload level and occurring according to the rotation speed of the main spindle. The numerical control apparatus ( ) comprises: a numerical control section ( ) for numerically controlling the movement of a spindle head ( ) and for outputting a rotation command; a spindle control section ( ) for controlling the rotation of a main spindle ( ); a preload change control section ( ) for changing the level of a preload applied to bearings ( ); and a correcting section ( ) for outputting correction data for correction of an axial displacement of the main spindle ( ) caused due to a change in the preload level and occurring according to the rotation speed of the main spindle ( ) to the numerical control section ( ) on the basis of the rotation command.

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Yamatokoriyama, Japan

Masaaki Yokoyama