Numerical controller having control mode switching function

A numerical controller having a control mode switching function for controlling a spindle by switching a control mode between a speed control mode for rotating a spindle motor according to a speed command and a position control mode for performing position control of the spindle motor according to a movement command, the numerical controller comprising:

• means for storing a position control start reference position of the spindle when the control mode is switched from speed control mode to position control mode;
• means for maintaining a rotational speed of the spindle motor immediately before switching to position control mode during execution of a position control mode switching command for switching the control mode from speed control mode to position control mode;
• position detection means for detecting a spindle position;
• differential value storage means for calculating and storing a difference between the spindle position at the start of execution of the position control mode switching command and the position control start reference position;
• means for calculating a position command pulse of the spindle on the basis of a program command and outputting the calculated position command pulse to a spindle motor driving unit, during the position control mode;
• compensation pulse calculation means for calculating a compensation pulse from a value stored in the differential value storage means;
• addition compensation means for adding the calculated compensation pulse to the calculated position command pulse and outputting the addition result;
• and
• spindle motor driving means for driving the spindle motor based on the addition result output by the addition compensation means, without stopping the spindle motor by using the means for maintaining the rotational speed of the spindle motor.