Patent ID: 8744612

Claim:
A numerical controller for machine tools that performs arc interpolation according to an arc radius and a feedrate commanded by a machining program, the numerical controller comprising: first allowable feedrate calculating means for calculating a first allowable feedrate, which is a feedrate of an arc to which servo position control is capable of responding, using an allowable frequency, which is a frequency to which servo position control is capable of responding, or an allowable angular speed, which is an angular speed to which servo position control is capable of responding, which is set in advance or specified by the machining program, and the commanded arc radius; comparison means for comparing the commanded feedrate with the calculated first allowable feedrate; and control means for performing speed control using the first allowable feedrate as the feedrate if the comparison means determined that the commanded feedrate is equal to or greater than the first allowable feedrate, wherein said first allowable feedrate calculating means calculates a speed F L using the following expression and sets the calculated F L as a first allowable feedrate; F L =2Π Rυ× 60 (mm/min) or F L =Rω× 60 (mm/min) where R is an arc radius, υ is a frequency to which servo position control is capable of responding, and ω is an angular speed to which servo position control is capable of responding.