Electric heating – Metal heating – Cutting or disintegrating
Patent
1994-03-22
1997-06-10
Evans, Geoffrey S.
Electric heating
Metal heating
Cutting or disintegrating
219 6913, 36447404, B23H 102, B23H 720
Patent
active
056372400
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electrical discharge machining method for automatically changing machining conditions during machining operation and an electrical discharge machining apparatus for carrying out the method.
BACKGROUND ART
In a conventional electrical discharge machining apparatus, machining is generally performed in accordance with previously set machining conditions. In other words, machining is generally executed under initially set machining conditions without changing machining conditions, including voltage applied between an electrode and a workpiece, servo voltage which determines the electrode feeding speed, capacitance in the case where the apparatus uses a capacitor discharge power source, on/off-time for the voltage applied between the electrodes, etc., during the machining operation.
A method in which machining conditions are changed depending on a discharge state between electrodes during machining operation is disclosed in Japanese Patent Publication No. 63-17568, for example. In the machining method described in this document, the machining conditions are changed in a manner such that a storage device is provided beforehand with a data table stored with data of several kinds, the data stored in the storage device are selected on the basis of detected data from a detecting device for detecting the discharge state, and new machining conditions are determined by executing an arithmetic operation for the selected data.
According to the method described above, the data are selected from the data table of the storage device in accordance with the detected data, and the machining conditions are changed depending on the selected data, so that the change of the machining conditions are restricted by the contents of the data table. Since the machining conditions can be changed only by stages, the controllability is not satisfactory. If the data stored in the table are increased in quantity so that the machining conditions can be changed to reflect fine differences between the detected data, this will cause not only a problem that the storage capacity of the storage device is depressed but also a problem such as the drop of the processing speed.
DISCLOSURE OF THE INVENTION
The present invention provides an electrical discharge machining method and apparatus in which machining conditions are automatically updated so that detected data indicative of a discharge state agrees with a target value during machining operation.
An electrical discharge machining method according to the present invention comprises the steps of: storing storage means with initial machining conditions for controlling a discharge state between a machining electrode and a workpiece, a target value of detected data indicative of the discharge state, and a constant for deriving new machining conditions, detecting the discharge state between the machining electrode and the workpiece and outputting the detection data indicative of the discharge state, computing the deviation between the detected data and the target value, executing a predetermined arithmetic operation based on the constant and the deviation and successively updating said initial machining conditions to obtain the new machining conditions, and controlling the discharge state in accordance with the obtained new machining conditions. Further, the present invention provides the means for carrying out these individual steps.
According to the arrangement described above, the machining conditions are automatically updated so that the detected data indicative of the discharge state agrees with the target value during the electrical discharge machining operation, whereby an optimum discharge state is obtained.
In the case of a wire-cut electrical discharge machining apparatus, in particular, the discharge state varies depending on the workpiece material, workpiece shape, wire diameter, nozzle, gap in a machining fluid supply nozzle etc., so that the target value of the detected data for optimum machining also varies depending on the workpi
REFERENCES:
patent: 4559434 (1985-12-01), Kinoshita
patent: 4970363 (1990-11-01), Obara
patent: 5200905 (1993-04-01), Uemoto et al.
patent: 5267141 (1993-11-01), Morita et al.
patent: 5408064 (1995-04-01), Takahara
patent: 5453592 (1995-09-01), Takeuchi et al.
Izumiya Shunzo
Kawahara Akiyoshi
Evans Geoffrey S.
Fanuc Ltd.
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