Machine tool and controlling method thereof

A machine tool comprising:

• a tool supporting member relatively movable to a workpiece along a predetermined axis;
• a servo motor configured to drive said tool supporting member to said workpiece along said predetermined axis;
• a sizing sensor configured to measure a profile of said workpiece machined by said tool and to output a size deviation of measured values from a target profile;
• a position detector configured to detect at least one of a relative position of said tool supporting member to said workpiece along said predetermined axis and a rotational position angle of said servo motor;
• a servo driver configured to drive said servo motor and comprising:
• a first feedback control having an output based on said size deviation output from said sizing sensor and configured drive said servo motor to make said size deviation to zero;
• a second feedback control based on an output of said position detector,
• wherein said servo driver is configured to switch from control based entirely on said second feedback control to control based entirely on said first feedback control.