Multiwire electric discharge machine and multiwire electric discharge machining system

A multiwire electric discharge machine that comprises a cutting wire section including a plurality of cutting wires arranged in parallel and located in such a way as to face a workpiece, the plurality of cutting wires being stretched in parallel between a plurality of guide rollers by winding a single wire electrode around the plurality of guide rollers, and that cuts the workpiece by causing an electric discharge between the cutting wire section and the workpiece, the multiwire electric discharge machine comprising:

• a machining power source to apply a machining pulse voltage between the workpiece and the cutting wire section;
• and
• a wire breakage detector to detect breakage of the wire electrode, wherein
• the wire breakage detector is electrically connected to a wire electrode portion of the wire electrode stretched over a section from one location on a feeding side of the wire electrode to one location on an ejection side of the wire electrode,
• the wire breakage detector includes:
• a wire breakage detection circuit that is an electric circuit in which a wire breakage detection power source and a current limiting resistor are connected in series, the wire breakage detection power source supplying a direct current to the wire electrode portion at least while the workpiece is undergoing a cutting process;
• and
• a wire breakage determiner including a circuit, the wire breakage determiner being configured to determine breakage of the wire electrode based on a current flowing through the current limiting resistor,
• the wire breakage determiner includes:
• a binarization circuit to convert current flowing through the current limiting resistor into a binarized signal that is a low-level signal or a high-level signal according to whether current is flowing through the current limiting resistor;
• and
• a signal processing circuit to detect, based on the binarized signal, a state where current stops flowing through the current limiting resistor, and output a wire breakage signal indicating a result of determination on breakage of the wire electrode,
• when a state where current stops flowing through the current limiting resistor is able to be detected, the wire breakage determiner determines that the wire electrode is broken, and
• the signal processing circuit outputs the wire breakage signal based on a result of comparison between a predetermined threshold value and a signal obtained by passing the binarized signal through a low-pass filter.