Gain changing control system for a threading apparatus

A threading apparatus, comprising:

• a spindle;
• a tool mounted on said spindle;
• a head supporting said spindle;
• a rotation motor rotating said spindle;
• a servo-control rotation drive circuit driving said rotation motor based, on at least an input command value and a rotational position detection value;
• a feed motor feeding said head;
• a gain changing circuit selectively setting one of a plurality of gains;
• and
• a servo-control feed drive circuit driving said feed motor based on at least an input command value, a feed position detection value, and the gain set by said gain changing circuit;
• wherein said rotation motor and said feed motor are synchronously operated.

A method for operating a control circuit of a machine tool apparatus comprising a feed device for feeding a tool along a longitudinal axis and a rotation device for rotating a tool about the longitudinal axis, the control circuit controllably driving the feed device and the rotation device, the method comprising the steps of:

• inputting a feed command to the control circuit;
• determining a rotation command based on the input feed command;
• setting a first gain into the control circuit prior to initiating a machining operation of the machine tool apparatus;
• initiating the machining operation of the machine tool apparatus to machine a workpiece based on the feed command, the rotation command, and the first gain;
• machining the workpiece based on the feed command, the rotation command, the first gain during a starting period after initiating the machining operation;
• setting a second gain into the control circuit;
• and
• continuing the machining operation based on the feed command, the rotation command, and the second gain during a second period after the starting period.