Wire electric discharge machine with tension monitoring function

A wire electric discharge machine with a tension monitoring function, the wire electric discharge machine configured to relatively move a wire electrode and a workpiece while applying voltage to an electrode gap formed between the wire electrode and the workpiece in machining the workpiece by removal processing, the wire electric discharge machine comprising:

• a tension generation device configured to stretch the wire electrode between a pair of guides, and generate tension in the wire electrode;
• a first tension measurement device fixed on the wire electrode between the pair of guides, the first tension measurement device being configured to measure the tension of the wire electrode;
• and
• a tension controller connected to the first tension measurement device and to the tension generation device, the tension controller being configured to
• receive a tension value measured by the first tension measurement device,
• output a tension command value to the tension generation device such that the tension value is equal to a target value, and
• preset a range of tension of the wire electrode, the range corresponding to the target value,
• wherein the tension controller is configured to generate a warning signal in response to the tension command value, which is output in response to the tension value actually measured by the first tension measurement device, being not within the range of tension preset by the tension controller,
• wherein the wire electric discharge machine further comprises:
• a robot;
• and
• a second tension measurement device movably mounted on the wire electrode between the pair of guides, and the second tension measurement device being configured to measure the tension of the wire electrode,
• wherein the tension controller is further configured to determine whether the tension generation device or the first tension measurement device is broken on the basis of the tension of the wire electrode measured by the second tension measurement device, and
• wherein, in response to the warning signal,
• the robot moves the second tension measurement device to the wire electrode and mounts the second tension measurement device on the wire electrode between the pair of guides, and
• the second tension measurement device measures the tension of the wire electrode while the machining is stopped.