Machining control apparatus in a machine tool

A machining control apparatus in a machine tool, comprising:

• first and second headstocks disposed so as to face each other, said first and second headstocks having first and second workpiece spindles rotatably supported thereby, respectively, at least one of said headstocks being free to move only in the direction of the central axis of said workpiece spindles, said first and second workpiece spindles being connected to respective spindle driving motors, said first and second workpiece spindles having first and second chucks, respectively, and said chucks being openable and closable such that said chucks are able to hold and release a workpiece to be machined;
• first and second tool rests corresponding to said first and second headstocks, respectively, said tool rests being free to be moved in at least a direction perpendicular to said direction of said central axis of said first and second workpiece spindles;
• said machine tool being capable of performing first and second machining routines on one or more than one workpiece being held by and between said first and second workpiece spindles with said first and second chucks according to a machining program;
• a rotational speed digital detection means connected to said first and second workpiece spindles for detecting the rotational speed of said workpiece spindles and outputting the rotational speed of said workpiece spindles as digital signals;
• a rotational speed comparison and operation means for comparing said rotational speeds of said workpiece spindles on the basis of said digital signals outputted from said rotational speed digital detection means and outputting an operation signal;
• a spindle driving motor control means for controlling said first and second spindle driving motors according to said operation signal from said rotational speed comparison and operation means such that the rotational speeds of said first and second workpiece spindles are equal;
• a headstock feed control means for driving and controlling at least one of said first and second headstocks in said direction of said central axis of said workpiece spindles;
• a chuck drive and control means for driving and controlling the opening and closing of said first and second chucks;
• a tool rest cutting-off drive and control means for driving and controlling said first and second tool rests to cut-off a workpiece held between said first and second workpiece spindles;
• said first and second workpiece spindles having respective through holes therein such that said through holes penetrate said workpiece spindles in the direction of said central axis;
• and
• a workpiece pulling unit disposed on the opposite side of said chuck of at least one of said workpiece spindles such that a machined workpiece held by said workpiece spindle having said workpiece pulling unit is removed passing through the inside of said through hole.