Electric heating – Metal heating – Cutting or disintegrating
Patent
1983-01-05
1984-09-04
Paschall, M. H.
Electric heating
Metal heating
Cutting or disintegrating
219 69G, 219 69W, B23P 108
Patent
active
044699271
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a power source arrangement for wire-cut, electric discharge machining which provides for increased cutting speed during wire-cut, electric discharge machining.
In wire-cut, electric discharge machining, for example, as shown in FIG. 1, a transistor 3 is controlled to be turned ON and OFF by pulses from a pulse generator 4 and, when the transistor 3 is in the ON state, a capacitor 5 is charged via a resistor 2 from a DC power source 1 and then the charged voltage of the capacitor 5 is applied across a wire electrode 7 and a workpiece 6, thereby performing electric discharge machining. Reference numeral 8 indicates a contactor, and 9 and 10 designate guides.
The voltage across the wire electrode 7 and the workpiece 6, that is, the gap voltage undergoes such variations, for instance, as shown in FIG. 2. That is to say, discharge occurs after or during charging of the capacitor 5. Experimental results have revealed that the cutting speed increases with a decrease in the charging voltage of the capacitor. The reason for this has not been made sufficiently clear yet, but it is said that, for example, if the capacitor charging voltage is high, the gap between the wire electrode and the workpiece is enlarged by electric discharge machining, making it difficult for a discharge produced at a point to shift to another point.
One might consider lowering the voltage of the DC power source 1 so as to make the charging voltage of the capacitor 5 lower, but this would reduce the charging energy of the capacitor 5, making it impossible to enhance the cutting speed. Also it would be possible to increase the value of the resistor 2, but this would also have the defects of lowered charging speed and increased power loss.
SUMMARY OF THE INVENTION
The present invention overcomes such defects of the prior art as mentioned above and has for its object to improve the cutting speed by controlling the capacitor charging voltage.
According to the present invention, in a power source arrangement for wire-cut, electric discharge machining which applies the charged voltage of a capacitor across a wire electrode and a workpiece to perform electric discharge machining of the workpiece, an auxiliary switching element is connected in parallel to a switching element performing control of the charging of the capacitor and the auxiliary switching element is controlled in accordance with the terminal voltage of the capacitor, thereby making the terminal voltage of the capacitor optimum for the electric discharge machining.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram showing the principal part of a conventional power source arrangement for wire-cut, electric discharge machining;
FIG. 2 is waveform diagram showing, by way of example, a gap voltage;
FIG. 3 is a circuit diagram illustrating the principal part of an embodiment of the present invention;
FIG. 4 is a waveform diagram showing an example of a gap voltage as in FIG. 3;
FIG. 5 is a block diagram showing a pulse generator for use in the present invention; and
FIG. 6 is a diagram explanatory of setting levels.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
FIG. 3 illustrates a principal circuit of an embodiment of the present invention, which is identical with the prior art example of FIG. 1 with regard to a DC power source 11, a resistor 12, a transistor 13, a capacitor 15, a workpiece 16, a wire electrode 17, a contactor 18 and guides 19 and 20. However the arrangement is such that a gap voltage voltage-divided by resistors 21 and 22 is applied to a pulse generator 14, the transistor 13 is controlled by control pulses a from the pulse generator 14, the transistor 24 is controlled by pulses b and the charging of the capacitor 15 is controlled via a resistor 23.
Supplied with a voltage proportional to the gap voltage from the resistors 21 and 22, the pulse generator 14 detects that the charging voltage of the capacitor 15 has reached a predetermined value, and turns OFF the transistor 13, and
REFERENCES:
patent: 4347425 (1982-08-01), Obara
patent: 4387285 (1983-06-01), Obara
Izumiya Shunzo
Obara Haruki
Fanuc Ltd.
Paschall M. H.
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