Electric heating – Metal heating – Cutting or disintegrating
Patent
1989-05-05
1990-10-16
Pellinen, A. D.
Electric heating
Metal heating
Cutting or disintegrating
219 6913, B23H 704
Patent
active
049637118
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for detecting an electric discharge position between a workpiece and a wire electrode in a wire electric discharge machine.
Generally known are various methods for detecting an electric discharge position in an electric discharge machining apparatus. These methods include a method (see Japanese Patent Disclosure No. 59-47124) in which the electric discharge machining position is detected by measuring the propagation time of pressure waves produced when electric discharge is caused, a concentrated electric discharge detecting method (see Japanese Patent Disclosure No. 59-30620) in which whether the electric discharge position is concentrated on one point is determined in accordance with discharge current waveforms, and a method (see Japanese Patent Disclosure No. 53-64899) in which the electric discharge position is detected by detecting the variation of an electric resistance between a point of electric power supply to a wire electrode and an electric discharge point.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an electric discharge position detecting device of a wire electric discharge machine, capable of accurately detecting an electric discharge position with a relatively simple arrangement, based on a novel principle of operation.
In order to achieve the above object, according to the present invention, an electric discharge position detecting device used in a wire electric discharge machine, in which an electric current is supplied from an electric discharge machining power source to a wire electrode through first and second conductors located above and below a workpiece, respectively, comprises: first and second detecting means for detecting the differentials of electric currents flowing through the first and second conductors, respectively; and third detecting means for detecting the difference between output signals from the two detecting means to generate an output signal indicative of an electric discharge position.
According to the present invention, as described above, the electric discharge position is always detected during electric discharge machining, in accordance with the difference between the differentials of the electric currents flowing through the conductors located above and below the workpiece, individually. Accordingly, the electric discharge position can be detected with a relatively simple arrangement, and the occurrence of concentrated electric discharge can be easily discriminated. Thus, the wire electric discharge machine can be controlled to prevent the wire electrode from being broken by concentrated electric discharge.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic circuit diagram showing the principle of operation of an electric discharge position detecting device according to one embodiment of the present invention;
FIG. 2 is a block circuit diagram showing the electric discharge position detecting device and peripheral elements associated therewith; and
FIG. 3 is a timing chart showing signal waveforms at various parts of the electric discharge position detecting device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In an electric discharge machining power source 3 for producing a machining pulse voltage, as shown in FIGS. 1 and 2, a negative output terminal is connected to an upper conductor 4 and a lower conductor 5 by means of a first lead wire 101 and a second lead wire 102, respectively, one end of the second lead wire 102 being connected to the terminal end of a first section 101a of the first lead wire at a junction P, while a positive output terminal is connected to a workpiece 2 by means of a third lead wire 103. Both conductors 4 and 5 are guided by wire guides 6 and 7 and a guide roller 8, and are in contact with a wire electrode 1 which penetrates a groove or hole 2a formed in the workpiece 2. First and second coils 9 and 10 for detecting discharge currents i1 and i2 flowing through the conductors 4 and 5, respectively, are arranged facing the fi
REFERENCES:
patent: 4329558 (1982-05-01), Martin
patent: 4575605 (1986-03-01), Martin
Evans Geoffrey S.
Fanuc Ltd.
Pellinen A. D.
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