US Patent No. 9,950,378

WIRE ELECTRIC DISCHARGE MACHINE


Patent No. 9,950,378
Issue Date April 24, 2018
Title Wire Electric Discharge Machine
Inventorship Tomoyuki Furuta, Yamanashi (JP)
Shinji Yoda, Yamanashi (JP)
Akiyoshi Kawahara, Yamanashi (JP)
Yasuo Nakashima, Yamanashi (JP)
Assignee FANUC CORPORATION, Yamanashi (JP)

Claim of US Patent No. 9,950,378

1. A wire electric discharge machine which comprises an auxiliary discharge circuit, configured to apply a voltage to an inter-electrode gap between an electrode and a workpiece, thereby inducing electric discharge, and a main discharge circuit configured to supply a machining current, and machines the workpiece by repeating a cycle in which the main discharge circuit is activated and stopped after the auxiliary discharge circuit is activated, the wire electric discharge machine comprising:a discharge delay time measuring unit configured to measure a discharge delay time, which is a duration without electric discharge such that a machining voltage is applied from the auxiliary discharge circuit to the inter-electrode gap,
wherein
a short-circuit machining current is supplied from the main discharge circuit to the inter-electrode gap when a result of measurement by the discharge delay time measuring unit is zero after a lapse of a predetermined short-circuit determination period since a start of an application of the machining voltage to the inter-electrode gap by the auxiliary discharge circuit,
no machining current is supplied from the main discharge circuit to the inter-electrode gap or a machining current lower than or equal to the short-circuit machining current is supplied when electric discharge is generated and the discharge delay time is less than a reference value after the short-circuit determination period,
a normal machining current equal to or higher than the short-circuit machining current is supplied from the main discharge circuit to the inter-electrode gap when electric discharge is generated and the discharge delay time is not less than the reference value after the short-circuit determination period, and
the machining current applied to the inter-electrode gap when electric discharge is generated and the discharge delay time is less than the reference value after the short-circuit determination period, is lower than the normal machining current applied to the inter-electrode gap when electric discharge is generated and the discharge delay time is not less than the reference value after the short-circuit determination period.