Method for controlling a machine tool and apparatus therefor

An apparatus for controlling a machine tool in which a work mounted on a table is machined through relative movement in X, Y and Z axis directions between the table and a main spindle, comprising:

• measuring means containing an emitting element and a photosensitive element provided on said table in which laser beam is irradiated from said emitting element towards said photosensitive element,
• a measuring tool which is formed with an interrupting portion of the laser beam shaped as a portion of circular cone form and is attached to said main spindle and can move towards the laser beam in the direction substantially at right angle therewith a relative movement between the measuring tool and the table and interrupt said laser beam,
• delivering means of detection signal of interruption generated at the moment when said measuring tool has interrupted said laser beam,
• position detecting means for detecting coordinate values for said respective three axes upon receiving said detection signal of interruption, and
• operating means in which operation processing of the difference between said measured coordinate value for each of the three axes and the measured coordinate value for each of the three axes measured before similarly is performed so as to obtain a displacement value between said main spindle and said table and the values for correction of positions of the main spindle and/or the table based on said obtained displacement value, wherein
• said machine tool is controlled with measurement of position being performed based on the obtained data.