Method of synchronous control of spindle motor and feed motor

A method of control of a spindle servomotor during machining, with a feed servomotor movably connected to the spindle servomotor such that the feed servomotor translationally moves the spindle servomotor along a longitudinal axis of the spindle servomotor, wherein the spindle servomotor has a torque limit versus rotational speed function curve represented by a straight line over a first speed range and a hyperbola over a second speed range, said method comprising the step of:

• (a) detecting a rotational speed of the spindle servomotor;
• (b) moving the spindle servomotor along a longitudinal axis with a translational speed determined by a speed of the feed servomotor;
• and
• (c) controlling the speed of the spindle servomotor in response to said torque limit function curve such that the spindle servomotor is accelerated over said first speed range along a straight line to have a constant torque and over said second speed range along a hyperbola line to have a decreasing torque so as to maintain a maximum torque of said spindle servomotor as said spindle is moved longitudinally.