Wire electrical discharge machine and control method

A wire electrical discharge machine for machining a workpiece by generating electrical discharge at an electrode gap formed between the workpiece and a wire electrode while moving the wire electrode relative to the workpiece, comprising:

• a control unit including a processor;
• and
• a storage unit, the storage unit storing instructions to cause the processor to control:
• a detection unit for detecting a contact state in which the wire electrode contacts the workpiece, and a contact release state in which the wire electrode that is in the contact state is separated from the workpiece;
• a vibration unit for, if the contact state is detected during machining of the workpiece, stopping relative movement of the wire electrode and vibrate the wire electrode about a stop position at which the relative movement of the wire electrode has been stopped;
• a relative movement control unit for resuming relative movement of the wire electrode if the contact release state is detected until a predetermined time elapses from when the contact state has been detected or until a number of times that the wire electrode is vibrated reaches a predetermined number of times;
• and
• a determination unit for determining whether or not the wire electrode will contact the workpiece when the wire electrode moves backward from the stop position along a machining groove formed in the workpiece,
• wherein the relative movement control unit relatively moves the wire electrode so as to move backward by a set distance from the stop position along the machining groove if the contact release state is not detected until the predetermined time elapses from when the contact state has been detected or until the number of times that the wire electrode is vibrated reaches the predetermined number of times, and if it is determined that the wire electrode will not contact the workpiece when the wire electrode moves backward from the stop position.