Control system for synchronized operation of machine tool motors

A speed control system for synchronizing the operation of motors in a machine tool for performing a tapping operation on a workpiece, which speed control system comprises:

• first operation control section means for controlling a spindle drive motor which rotates the spindle of the machine tool, the spindle being configured for holding a tap for the tapping operation;
• and
• second operation control section means for controlling a motor which moves the workpiece and the spindle relative to one another axially of the spindle;
• wherein said first operation control section means includes a speed command voltage generating circuit having down-counter means for storing the number of tap revolutions, the stored value being decremented by one count each time the tap makes one revolution, and having function generator means for producing a speed command signal VCMD in accordance with the count value stored by the down-counter means, position signal generating circuit means for producing a position signal indicative of the rotational position at which the spindle is to be stopped, speed control unit means for controlling the spindle drive motor in response to a speed control unit means input signal, and changeover switch means for selecting, in accordance with the count value stored in the down-counter means, one of the speed command signal VCMD and the position signal for use as the speed control unit means input signal;
• and
• wherein said second operation control system means includes means for moving the workpiece and the spindle relative to one another at all times at a speed which is the product of the rotational speed of the spindle and the pitch of the threads on the tap that performs the tapping operation.