Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2008-01-29
2008-01-29
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
Reexamination Certificate
active
11498838
ABSTRACT:
An electric discharge machining apparatus capable of precisely detecting the electric discharge in a case of performing machining by minute machining energy such as in finish machining. A voltage is applied between a tool electrode and a workpiece by repeating ON/OFF of a switching element to charge a stray capacitance between the electrodes to cause electric discharge between the electrodes by the charged voltage. The electric discharge between the electrodes in the electric discharge machining by the minute machining energy is detected. The current between the electrodes is detected by integrating an output of a sensor coil. An offset component superposed in the output of the integrator by a low-pass filter is extracted. The extracted offset component is eliminated from the output of the integrator by a differential amplifier. An output of the differential amplifier is compared with a reference value to detect the electric discharge.
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Extended European Search Report mailed Dec. 12, 2006 in corresponding European Patent Application No. 06254014-1262.
Murai Masao
Nakashima Yasuo
Evans Geoffrey S.
Fanuc Ltd.
Staas & Halsey , LLP
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