PURPOSE:To enable the stable control of wire tension by providing a loading body shifting via a movable roller and a tension setting instruction on an arm with one end thereof so supported as to turn freely, and causing the shift of the loading body depending upon the motion of the arm. CONSTITUTION:A wire 1 after a wire reel 1 travels via a braking roller 9, a movable roller 7, a workpiece 3 and the like, and is recovered in a wire recovery box 18. An arm 6 supporting the movable roller 7 is so supported about a fulcrum 6-1 as to turn freely, and a mobile loading body 8 is so provided on the arm 6 as to be freely movable. Depending upon the output of a positioning sensor 14, therefore, it becomes possible to move the mobile body 8 so that a clockwise moment due to the mobile loading body 8 will balance with a counter-clockwise moment due to the wire 1, thereby enabling making control for keeping the wire 1 tensioned to a proper value.
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