A wire cut electrodischarge machine tool, more particularly to a wire cut electrodischarge machine tool which, when disconnection of an electrode wire occurs during the electrodischarge machining, repairs the disconnected end at a repair position apart from the electrodischarge machining region, then automatically lays the electrode wire between upper and lower heads having built-in wire guides to automatically prepare for the start of electrodischarge machining on the workpiece.

There has already been proposed a wire cut electro-discharge machine tool using an electrode wire of a wire shape or strip shape, which is provided with, for times when the electrode wire breaks during the machining, a clamp mechanism for clamping an electrode wire portion on a feeding side and an electrode wire feed mechanism for moving the electrode wire so that the end of electrode wire portion on the feed side coincides with a preset position and which thus enables automation of the insertion of the electrode wire portion of the feed side to the work (See Japanese Unexamined Patent Publication No. 56-3146). This known wire cut electrodischarge machine tool controls the wire cut electrodischarge machining process and the aforementioned machining restart preparation process at the time of electrode wire disconnection by means of a CNC device (computer numeral control device) using a microcomputer.

However, in a wire cut electrodischarge machine tool due to the electrodischarge action between the electrode wire and workpiece, or the tilted running of the electrode wire during taper hole machining, when the electrode wire breaks, the disconnected portion tends to be curved or rough surfaced. Therefore, often it is impossible to correctly refeed the disconnected electrode wire end through the wire inserting hole of the workpiece without some repair thereof.