Patent ID: 6998562

Claim:
A controller for a wire electrical discharge machine that supplies discharge pulse current between a wire electrode and a workpiece to perform electrical discharge machining while causing relative motion between the wire electrode and the workpiece, the controller comprising: discharge pulse counting means for counting the number of supplied discharge pulses every preset time; moving means for causing relative motion between the wire electrode and the workpiece along a machining path according to motion commands; reference discharge pulse count storage means for storing a reference number of discharge pulses per unit time; discharge pulse count comparing means for comparing a value obtained from the discharge pulse counting means with a value obtained from the reference discharge pulse count storage means and obtaining a ratio therebetween; feed pulse calculating means for obtaining a distance by multiplying a relative movement of the wire electrode with respect to the workpiece, which is determined from a set feed speed and said preset time, by the ratio and for sending the obtained distance to the moving means as a movement command every said preset time; discharge start point detecting means for detecting a discharge start point by detecting occurrence of a discharge; machining travel distance calculating means for calculating a machining travel distance from the discharge start point; comparing means for comparing the machining travel distance with a predetermined distance; short circuit detecting means for detecting a short circuit between the wire electrode and the workpiece; and feed speed setting switching means for switching a set feed speed; wherein, according to a comparison result obtained from the comparing means and to detection output from the short circuit detecting means, the feed speed setting switching means switches to a low feed speed when a short circuit is detected while the machining travel distance is within the predetermined distance, and switches to a normal feed speed when the machining travel distance exceeds the predetermined distance.