Automatic wire-threading device

An automatic wire-threading device of a wire electric-discharge machining device, the automatic wire-threading device comprising:

• a wire feed motor that drives a wire feed roller in a feeding direction;
• a wire-feed-motor control unit that outputs a feeding-direction rotation-speed reference to the wire feed motor at a time of a threading operation of a wire electrode, and that reduces torque in a feeding direction when a detected rotation speed of the wire feed roller is larger than the feeding-direction rotation-speed reference;
• a wire collecting motor that drives a wire collecting roller in a collecting direction;
• and
• a wire-collecting-motor control unit that outputs a predetermined wire-collecting-roller speed reference to the wire collecting motor to collect a wire, wherein
• the automatic wire-threading device performs a threading operation of the wire electrode from the wire feed roller to the wire collecting roller, and
• the wire-feed-motor control unit controls torque of the wire feed motor based on a feeding direction torque limiting value and a winding-back direction torque limiting value, an absolute value of the winding-back direction torque limiting value being smaller than an absolute value of the feeding direction torque-limiting value.