Abstract: There are determined by measurements: the maximum -A of the positional displacement, which is caused by a deflection when a machining point is moved in a +X direction; and a movement command D in effect until the machining point is reversed to a -X direction while the maximum deflection -A is maintained and the deflection A in the reverse direction is produced. It is assumed that the deflection proportionally changes from -A to +A while the movement command is outputted by D, that is, while the actual position of the machining point is moved by (D-2A). The correction amount is determined on the bases of the proportion of two times the deflection A with respect to (D-2A) and the movement command value after the reversal of the moving direction, and is added to the movement command value so that the resultant sum is outputted as the movement command value.

Abstract: A method of canceling a short circuit in a wire cut electric discharge machine, capable of speedily and surely canceling the short circuit generated in not only the wire advancing direction but also the perpendicular direction to the advancing one. When the short circuit is detected, the wire is reversed by determined distance L.sub.O, and if the short circuit is not canceled at that time, it is determined that the short circuit occurs in the perpendicular direction to the wire advancing one sequentially, machining profiles and the wire position are determined so that the optimum reversible control can be performed, thus the reversing direction and distance of the wire being determined. Further, the optimum reversible control is carried out on the basis of the determined reversing direction and distance, and the wire is returned to the position where the short circuit is initially detected if the cancellation of the short circuit is detected, thus the electric discharge machining being restarted.