JP2000079514A - Electric discharge machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce electrode consumption and prevent reduction in machining speed even when current pulse interruption frequently occurs. SOLUTION: This device is provided with a voltage generating means 3 for applying pulse voltage to a clearance between an electrode 1 and a workpiece 2 facing each other to perform electric discharge machining, an electrostatic capacity detecting means 30 for detecting the electrostatic capacity of the clearance, a voltage polarity switching means 20 for switching the electrode 1 to an cathode of the voltage generating means and switching the workpiece 2 to an anode of the voltage generating means 3, and a control means 50 for switching the voltage polarities of the electrode 1 and the workpiece 2 based on the detected values of the electrostatic capacity detecting means 30, using the voltage polarity switching means 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining apparatus for performing electric discharge machining of a workpiece using a simple electrode.

[0002]

2. Description of the Related Art A conventional electric discharge machine will be described with reference to FIG. In FIG. 121, 1 is an electrode, 2 is a workpiece, 3 is a variable power supply capable of varying a voltage value, 4 is a variable resistor capable of varying a resistance value for current limiting, 5 is a switching element for supplying a pulse voltage, 6 is a switching element 5
A switching control circuit for controlling the switching of the capacitor, 7 is a variable capacitor element capable of varying the capacitance, 8 is an electrode 1
And a floating capacitance 9 in a machining gap (hereinafter referred to as a gap) formed by the workpiece 2 and a discharge detection circuit 9 for detecting the occurrence of a discharge between the gaps by the fall of the voltage.

Next, the operation of the electric discharge machine configured as described above will be described with reference to FIGS. When the switching element 5 is turned on by the switching control circuit 6, the voltage determined by the variable power supply 3 is supplied between the electrodes formed between the electrode 1 and the workpiece 2.
The discharge detection circuit 9 detects the discharge on condition that the discharge occurs between the electrodes and the applied voltage between the electrodes becomes lower than a predetermined voltage level, and sends the detected value to the switching control circuit 6.

The switching control circuit 6 maintains the ON state of the switching element 5 for a predetermined time from the occurrence of the discharge, supplies a current pulse only for the ON time ton, and then pauses the switching element 5 for the OFF time toff. The current shown in FIG. By performing the above power supply control, electric discharge machining proceeds.

[0005]

However, in the electric discharge machine configured as described above, the current pulse may be interrupted on the way as shown in FIG. Such a phenomenon is referred to as a pulse break, which increases the consumption of the electrode 1 and decreases the processing speed.

[0006] The pulse break is (1) as the peak value of the current pulse is smaller, that is, as the limiting resistance R is larger,
(2) It is known that the more the circuit is capacitive, that is, the larger the capacitance of the capacitor 7 and the stray capacitance 8 between the electrodes, and the smaller the inductance of the circuit, the more easily the circuit is generated. A combination of constants is selected.

However, if the processing area is large or the processing area increases during processing, the floating capacitance 8 formed between the poles increases, and even if an optimum combination of circuit constants is selected, the pulse The frequency of cutting increases. For example, 1
In the case of machining a finish machining area with a surface roughness of 5 μm Rmax or less in a machining area of about 000 mm ² or more, it becomes difficult to prevent pulse breakage, and the pulse 1 sharply increases the consumption of the electrode 1. There has been a problem that deterioration is caused, processing efficiency is reduced, and processing speed is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides an electric discharge machining apparatus that reduces electrode consumption and prevents a reduction in machining speed even when current pulses are frequently interrupted. With the goal.

[0009]

According to a first aspect of the present invention, there is provided an electric discharge machining apparatus comprising: a voltage generating means for applying a pulse voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining; Capacitance detection means for detecting capacitance; voltage polarity switching means for switching the workpiece to an anode of the voltage generation means while using the electrode as a cathode of the voltage generation means; Control means for switching the voltage polarity of the electrode and the workpiece using the voltage switching generation means based on the detection value of the means.

According to a second aspect of the present invention, there is provided an electric discharge machining apparatus which performs a discharge machining by applying a pulsed voltage to a gap between an opposing electrode and a workpiece, and which can vary a voltage value. It is provided with capacitance detecting means for detecting the capacitance of the gap, and control means for changing a voltage value generated by the variable voltage generating means based on a detection value of the capacitance detecting means. Things.

According to a third aspect of the present invention, there is provided an electric discharge machining apparatus for applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining, and detecting a capacitance of the gap. Capacitance detecting means, a peak value changing means for changing a peak value of a current flowing in a gap between the electrode and the workpiece, and a peak value changing means based on a detection value of the capacitance detecting means. Control means for controlling the current flowing through the gap.

According to a fourth aspect of the present invention, there is provided an electric discharge machining apparatus for applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining, and detecting a capacitance of the gap. Capacitance detecting means, variable capacitance means for changing a capacitance value of a gap between the electrode and the workpiece, and the variable capacitance based on a detection value of the capacitance detecting means. Control means for changing the capacitance value of the means.

According to a fifth aspect of the present invention, there is provided an electric discharge machining apparatus comprising: a voltage generating means for applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining; Average voltage reference means for determining the average voltage value of the gap, average voltage control means for controlling the average voltage to be a reference value based on the average voltage reference means, and static voltage for detecting the capacitance between the electrodes. And a control means for changing and controlling the voltage value of the average voltage reference means based on the detection value of the capacitance detection means.

According to a sixth aspect of the present invention, the capacitance detecting means of the electric discharge machine is a measuring means for measuring a rise time of a voltage in the gap.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a circuit diagram of an electric discharge machine according to an embodiment of the present invention, and FIG. 2 is a circuit diagram for measuring a rise time of a pulse voltage. In the figure, the same reference numerals as those in the related art indicate the same or corresponding parts, and the description thereof will be omitted. In FIG. 1, a variable power supply 3 is connected to one end of a variable resistor 4 via a switching unit 20 as a voltage polarity switching unit.
The workpiece 2 and one end of the variable capacitor 7 are connected. The switching unit 20 switches the polarity of the variable power supply 3 and includes contacts A, A and contacts B, B. When one of the contacts A, A (B, B) is closed, the other contact is used. B, B (A, A) are configured to be open.

Reference numeral 30 denotes a measuring circuit for measuring the rise time of the pulse voltage between the poles as capacitance detecting means using the capacitance between the poles.
For example, the switching unit 20 is operated by increasing the voltage rise time to switch the polarity of the variable power
Is a power supply controller for controlling the polarity of the cathode to be a cathode and reducing the voltage of the voltage power supply 3.

Here, the measurement circuit 30 measures the rise time of the voltage instead of the capacitance C between the electrodes because the voltage rise time tr changes in accordance with the capacitance between the electrodes. Electrostatic capacitance C and voltage rise time tr
(Tr ₁ , tr ₂ ... Trn), the following (1) to
(3) is obtained, and by solving the following equation, the interelectrode capacitance is obtained from the voltage rise time. Vr ₁ = E · (1−e ^{−t1 / RC} ) (1) Vr ₂ = E · (1−e ^{−t2 / RC} ) (2) tr = t ₂ −t ₁ (3) where R is a circuit the resistance value (current limiting resistor), E is the voltage value of the voltage source 3, t ₁ is the rise time of the voltage application to Vr _1, t ₂ is the rise time of the voltage application to Vr _2.

The reason why the polarity of the electrode 1 is changed to a cathode opposite to that of a normal electrode by increasing the interelectrode capacitance is that it is known that a waveform having a shorter pulse width consumes less electrode. . For example, for a processing area of about 10,000 mm ² or more, when processing is performed in a state where the pulse of the electrode 1 frequently occurs at the anode, the polarity of the electrode 1 is set to 0.01 to
This is because, when a capacitor of about 0.1 μF is added between the poles and processing is performed with a capacitor current waveform having a short pulse width of about 0.1 to 0.5 μs, the electrode 1 is less consumed and the processing speed is higher. .

In the measuring circuit 30 shown in FIG.
Is a reference voltage setting device, 35 and 36 are comparators for comparing the voltage at the time of voltage rise with the reference voltage, 37 is a reference count pulse generator, 38 is an AND circuit, and 39 is a NAND circuit.
The circuit, 40 is a counter for counting the voltage rise time, and 41 is a latch circuit for holding the output of the counter 40.

Next, the operation of the electric discharge machine configured as described above will be described with reference to FIGS. FIG. 3 is a time chart showing the operation of the measurement circuit. First, while the contacts A, A of the switching unit 20 are closed, and the contacts B, B are kept open, the switching control circuit 6 turns on the switching element 5, so that the voltage value of the variable power supply 3 It is supplied between the poles formed between the workpieces 2.

The discharge detection circuit 9 detects a discharge when a discharge occurs between the electrodes and the applied voltage between the electrode 1 and the workpiece 2 becomes lower than a predetermined voltage level, and controls the detection result by switching control. Send to circuit 6. The switching control circuit 6 turns on the switching element 5 only for a time ton from the occurrence of the discharge, raises the voltage between the electrodes as shown in FIG.
Only off is turned off, and the switching operation is repeated.

In the measuring circuit 30, the reference voltage setting device 33 outputs the low voltage level Vr ₁ when the voltage pulse rises to the comparator 35, and the reference voltage setting device 34 similarly outputs the high voltage level Vr ₂ to the comparator 36. ing. The comparators 35 and 36 compare the reference voltages Vr ₁ and Vr ₂ with the inter-electrode voltage. When the inter-electrode voltage is higher than Vr ₁ and Vr ₂ , the output becomes “H”. Sent to

As shown in FIG. 3A, the output a of the AND circuit 38 has a rise time t when the voltage between the electrodes changes from Vr1 to Vr2.
A pulse voltage having a width corresponding to r ₁ , tr ₂ , and tr ₃ is output. The output a of the AND circuit 38 is sent to the NAND circuit 39 together with the output of the reference count pulse generator 37 to output a pulse train b. The rise time is
It has a relationship of tr ₂ > tr ₁ > tr ₃ .

The counter 40 counts the pulse train b and outputs an output corresponding to the rising time to a latch circuit 41.
Is the rise time t at the fall timing of the output a.
r _1, tr _2, tr output value corresponding to _{3 E 1, E 2, E} 3 (E
₂ > E ₁ > E ₃ ) and outputs the signal c and holds it until the next voltage application time. Although this signal (c) is a digital quantity, it is shown as an analog quantity in the figure for convenience of explanation.

Here, the voltage rising time tr ₁
If (tr ₃ ) is shorter than the predetermined time tp, that is, if the capacitance between the electrodes is low, the switching unit 2
0 indicates that the output voltage value of the variable power supply 3 is inversely proportional to the output value E ₂ of the measurement circuit 30 by the voltage controller 30 in a state where the contacts A, A are closed and the contacts B, B are kept open. By controlling, the current shown in FIG. 13 flows between the poles.

On the other hand, if the voltage rising time tr ₂ is longer than the predetermined time tp, that is, if the capacitance between the electrodes is high, the switching unit 20 switches the contacts A, A
And the contacts B and B are closed, the polarity of the electrode 1 is set to the cathode, and the power supply voltage controller 12 outputs the output voltage of the variable power supply 3 almost in inverse proportion to the output value E ₂ of the measurement circuit 30. By controlling the value by the voltage controller 30, the voltage / current waveform between the electrodes shown in FIG. 4 is obtained.

The polarity of the electrode 1 becomes a cathode, and the applied voltage between the electrodes becomes lower, so that the distance between the electrodes is reduced in order to continue the discharge. Therefore, the capacitance between the electrodes increases.
Due to the increase in the capacitance, the pulse current after the discharge of the capacitor is reliably cut off as shown in FIG. 4, and the workpiece is processed with a uniform current waveform of only the discharge of the capacitor. Therefore, the electrode consumption is reduced and the processing speed is increased. Furthermore, even in the case of processing where the processing area changes during processing and the frequency of pulse cuts increases, it is possible to control so that a uniform capacitor discharge current can be obtained, thereby improving the processing speed, processing accuracy, etc. it can. In the above-described embodiment, when the voltage rise time tr increases, the voltage polarity of the electrode 1 is switched from the anode to the cathode, and then the voltage value between the electrodes is decreased. However, the voltage polarity is not switched. Alternatively, only the voltage between the electrodes may be reduced.

Embodiment 2 Another embodiment of the present invention will be described with reference to FIG. FIG. 5 is a circuit diagram of an electric discharge machine according to another embodiment of the present invention. In FIG. 5, reference numeral 60 denotes a resistance switching unit as a peak value changing means for changing the peak value of the current flowing between the poles.
Is a resistor R between the variable power supply 3 and the switching element 5.
1, R2 and R3 are normally open contacts 60D, 60E and 6 respectively.
0F, and the resistance values of the resistors R1, R2, and R3 have a relationship of R1>R2> R3. Reference numeral 70 denotes a resistance controller that changes the peak value of the discharge current pulse by closing one of the normally open contacts 60D, 60E, and 60F according to the rise time of the voltage.

Next, the operation of the electric discharge machine configured as described above will be described with reference to FIGS. If the capacitance between the electrodes is low, the measuring circuit 30 detects the voltage rise time tr
Upon detecting ₁ , the resistance controller 70 closes the normally open contacts 60F, opens the normally open contacts 60D and 60E, inserts the resistor R3 into the circuit, and controls the current peak value without much limiting. I do. Since it is almost the same as the first embodiment,
Description is omitted.

On the other hand, when the capacitance between the electrodes increases, the measuring circuit 30 measures the lengthened voltage rising time tr ₂ and sends the detected value to the resistance controller 13. The resistance controller 13 closes the normally open contact 60D, inserts the resistor R1 into the circuit, and controls the peak value of the current sufficiently. In the case of the voltage rise time tr ₃ , the normally open contact 6
0E is closed, the normally open contacts 60D and 60F are opened, and the resistor R2 is inserted into the circuit to control the current peak value slightly to control.

By reducing the peak value of the current between the poles,
In order to continue the discharge, the distance between the electrodes is reduced, so that the capacitance between the electrodes is increased. Due to the increase in the capacitance, the pulse current after the discharge of the capacitor is reliably cut off as shown in FIG. 6, and the workpiece is processed with a uniform current waveform of only the discharge of the capacitor. Therefore, the electrode consumption is reduced and the processing speed is increased.

In the above embodiment, when the voltage rise time tr is increased, only the peak value of the current between the electrodes is decreased. However, after the voltage polarity of the electrode 1 is switched from the anode to the cathode, the voltage is changed from the anode to the cathode. The peak value of the current may be reduced.

Embodiment 3 Another embodiment of the present invention will be described with reference to FIG. FIG. 7 is a circuit diagram of the electric discharge machine. In FIG. 7, reference numeral 80 denotes a capacitor switching unit as variable capacitance means for changing the capacitance between the electrodes.
The capacitor switching unit 80 includes a capacitor C1,
C2 and C3 are normally open contacts 80D, 80E and 80F, respectively.
And capacitors C1, C2, C3
Has a relationship of C1>C2> C3, and 90 indicates that when the voltage rise time increases, one of the normally open contacts 80D, 80E, and 80F is closed in accordance with the rise time, and discharge occurs. This is a capacitor controller that changes and controls the peak value of the current pulse.

Next, the operation of the electric discharge machine configured as described above will be described with reference to FIGS. If the capacitance between the electrodes is low, the measuring circuit 30 detects the voltage rise time tr
₁ and the capacitor controller 90 sets the normally open contact 80F
Is closed, the normally open contacts 80D and 80E are opened, and the capacitor C3 is inserted between the poles for control. Since it is almost the same as the first embodiment, the description is omitted.

On the other hand, when the capacitance between the electrodes increases, the measuring circuit 30 determines that the voltage rising times tr ₂ and tr ₃ have become longer.
And sends the detected value to the capacitor controller 90. The capacitor controller 90 determines the voltage rise time t
In the case of r ₂ serves to close the normally open contact 80E, the normally open contacts 80D, and the open 80F controls by inserting a capacitor C2 to the circuit. Also, the voltage rise time tr
_In the case of ₃ , control is performed by closing the normally open contact 80D, opening the normally open contacts 80E and 80F, and inserting the capacitor C1 between the poles.

As shown in FIG. 8, the pulse current after the discharge of the capacitor is reliably interrupted by the increase in the rise time of the voltage, and the workpiece is processed by a uniform current waveform of only the discharge of the capacitor. Therefore, the electrode consumption is reduced and the processing speed is increased.

In the above embodiment, when the voltage rise time tr is increased, the capacitance between the electrodes is increased. However, after the voltage polarity of the electrode 1 is switched from the anode to the cathode, the voltage between the electrodes is changed. The capacitance between them may be increased.

Embodiment 4 FIG. Another embodiment of the present invention will be described with reference to FIG. FIG. 9 is a circuit diagram of a discharge device showing another embodiment of the present invention. This embodiment is applied to the average voltage servo method, and the average voltage servo method uses other state quantities that can be regarded as equivalent to the distance between the poles obtained from the voltage waveform between the poles. And that the average value of the voltage between the electrodes is proportional to the distance between the electrodes.

In FIG. 9, reference numeral 15 denotes a reference voltage controller for reducing the reference voltage value of the gap servo when the capacitance between the poles increases, and controlling the reference voltage value to be equal to the reference voltage value. An average voltage detector 17 for detecting an average voltage value during the processing of the motor; a drive controller 18 for controlling the distance between the electrodes so that the value detected by the average voltage detector 16 maintains the reference voltage value; Is a position driving device.

Next, the operation of the electric discharge machine configured as described above will be described with reference to FIGS. When the capacitance between the electrodes is low, the measuring circuit 30 detects the voltage rise time t.
r ₁ is detected, power control is performed in substantially the same manner as in the first embodiment, and feed control is performed so that the relative distance between the poles is constant according to the state between the poles. That is, the inter-electrode voltage detector 16 detects an average voltage value between the electrodes during machining, and the drive controller 17 maintains the machining voltage constant based on the average voltage value detected by the average voltage detector 16. for,
A signal for controlling the gap is sent to the position driving device 18. The position driving device 18 advances the electric discharge machining while driving the electrode 1 based on a command signal from the drive controller 17.

On the other hand, when the capacitance between the electrodes increases, the measuring circuit 30 determines that the voltage rising times tr ₂ and tr ₃ have become longer.
Is measured as in the first embodiment, and the detected value is sent to the reference voltage controller 15. The reference voltage controller 15
Based on the detection value of the measuring circuit 30, control is performed so as to decrease the reference voltage value of the gap servo and to decrease the average voltage value during machining.

Therefore, in order to continue the discharge by lowering the reference voltage between the electrodes, the distance between the electrodes is reduced, so that the capacitance between the electrodes is increased. Due to such an increase in the capacitance, the pulse after the capacitor discharge is surely cut off as shown in FIG. 10, and processing with a uniform current waveform of only the capacitor discharge is performed. Therefore, the electrode consumption is reduced and the processing speed is increased.

In the above embodiment, when the voltage rise time tr is increased, the reference voltage between the electrodes is decreased. However, after the voltage polarity of the electrode 1 is switched from the anode to the cathode, the voltage between the electrodes is reduced. May be reduced.

In the above-described embodiment, the measuring circuit 30 for measuring the rise time of the pulse voltage is used as the capacitance detecting means between the electrodes. However, as shown in FIG. The capacitance measurement unit 100 between the electrodes disclosed in the publication may be used. Capacitance measuring unit 100
Has a capacitor 121 for blocking a direct current, an oscillator 122 for oscillating an AC sine wave, and a resistor 123 having a relatively small resistance connected between the electrode 1 and the workpiece 2.

Further, the measuring circuit 30 according to the above embodiment is used.
Measured the rise time from the voltage Vr ₁ to Vr ₂ , but may measure the time from the start of the application of the voltage between the electrodes until the voltage reaches Vr ₂ as the rise time tr. In such a case, the number of comparators 25 and 26 can be reduced to one.

Further, the measuring circuit 30 according to the above embodiment is used.
Measured the rise time of the machining voltage pulse,
A configuration may be adopted in which the detection pulse voltage is applied during the period of the discharge pause, and the rise time of the detection pulse voltage is measured and controlled.

[0047]

According to the first aspect of the present invention, a voltage generating means for applying a pulsed voltage to the gap between the facing electrode and the workpiece to perform electric discharge machining, and a static electricity detecting means for detecting the capacitance of the gap. Capacitance detection means, voltage polarity switching means for switching the workpiece to the anode of the voltage generation means while using the electrode as the cathode of the voltage generation means, and voltage detection means based on the detection value of the capacitance detection means. Control means for switching the voltage polarity of the electrode and the workpiece using the voltage switching generating means, so that the discharge is continued by lowering the applied voltage between the electrodes, so that the distance between the electrodes is reduced. As a result, the pulse current after discharge of the capacitor is reliably cut off, and the workpiece can be machined by a uniform current waveform of only the discharge of the capacitor. Therefore, there is an effect that the electrode consumption is reduced and a reduction in the processing speed can be prevented.

According to the second aspect of the present invention, the pulse-like voltage is applied to the gap between the opposing electrode and the workpiece to perform electric discharge machining, and the variable voltage generating means can vary the voltage value. Capacitance detection means for detecting the capacitance, and a control means for changing the voltage value generated by the variable voltage generation means based on the detection value of the capacitance detection means,
Since the discharge is continued by lowering the applied voltage between the poles, the distance between the poles is reduced to increase the capacitance between the poles. The workpiece can be processed by the waveform. Therefore, there is an effect that the electrode consumption is reduced and a reduction in the processing speed can be prevented.

According to the third aspect of the present invention, a voltage generating means for applying a pulsed voltage to the gap between the facing electrode and the workpiece to perform electric discharge machining, and a capacitance for detecting the capacitance of the gap Detecting means, a peak value changing means for changing a peak value of a current flowing through a gap between the electrode and the workpiece, and a peak value changing means based on a detected value of the capacitance detecting means, Control means for controlling the flowing current, so that the peak value of the current between the poles is reduced and the discharge is continued, so that the distance between the poles is reduced to increase the capacitance between the poles, and the pulse after the discharge of the capacitor The current is reliably cut off, and the workpiece can be machined by a uniform current waveform of only the capacitor discharge. Therefore, there is an effect that the electrode consumption is reduced and a reduction in the processing speed can be prevented.

According to the fourth aspect, a voltage generating means for applying a pulsed voltage to the gap between the facing electrode and the workpiece to perform electric discharge machining, and a capacitance for detecting the capacitance of the gap Detecting means; variable capacitance means for changing a capacitance value of a gap between the electrode and the workpiece; and static capacitance of the variable capacitance means based on a detection value of the capacitance detecting means. Control means for changing the capacitance value increases the inter-electrode capacitance, reliably interrupts the pulse current after capacitor discharge, and allows the machining of the workpiece with a uniform current waveform of capacitor discharge only. it can. Therefore, there is an effect that the electrode consumption is reduced and a reduction in the processing speed can be prevented.

According to the fifth aspect, a voltage generating means for applying a pulsed voltage to the gap between the facing electrode and the workpiece to perform electric discharge machining, and the average of the gap between the electrode and the workpiece. Average voltage reference means for determining a voltage value; average voltage control means for controlling the average voltage to be a reference value based on the average voltage reference means; and capacitance detection for detecting the capacitance between the electrodes. Means, and control means for changing and controlling the voltage value of the average voltage reference means based on the detection value of the capacitance detection means, so that the discharge is continued by lowering the gap reference voltage. Since the distance between the poles is reduced, the capacitance between the poles increases, and the pulse current after the discharge of the capacitor is reliably cut off. it can. Therefore,
This has the effect of reducing electrode consumption and preventing a reduction in processing speed.

According to the sixth aspect, in addition to the effect of any one of the first to fifth aspects, the capacitance detecting means is a measuring means for measuring the rise time of the voltage in the gap, so that it can be simplified. There is an effect that the capacitance between the electrodes can be detected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an electric discharge machine according to an embodiment of the present invention.

FIG. 2 is a measurement circuit diagram shown in FIG.

FIG. 3 is a time chart showing an operation of the measurement circuit shown in FIG. 2;

4A and 4B are a voltage waveform diagram and a current waveform diagram between poles by the electric discharge machine of FIG.

FIG. 5 is a circuit diagram of an electric discharge machine according to another embodiment of the present invention.

6A and 6B are a voltage waveform diagram and a current waveform diagram between the electrodes by the electric discharge machine of FIG.

FIG. 7 is a circuit diagram of an electric discharge machine according to another embodiment of the present invention.

8A and 8B are a voltage waveform diagram and a current waveform diagram between the electrodes by the electric discharge machine of FIG.

FIG. 9 is a circuit diagram of an electric discharge machine according to another embodiment of the present invention.

10A and 10B are a voltage waveform diagram and a current waveform diagram between the electrodes by the electric discharge machine of FIG. 9;

FIG. 11 is a diagram showing a capacitance detection circuit between poles according to another embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a conventional electric discharge machine.

13A and 13B are a voltage waveform diagram and a current waveform diagram between the electrodes by the electric discharge machine of FIG.

14 is a diagram showing a voltage waveform and a current waveform between the electrodes when a pulse break occurs in the electric discharge machining apparatus of FIG. 12;

[Explanation of symbols]

1 electrode, 2 workpiece, 3 variable power supply (variable voltage generation means, voltage generation means), 15 reference voltage controller (average voltage reference means, average voltage control means), 20 switching unit (voltage polarity switching means), 30 Measurement circuit (capacitance detection means), 60 resistance switching section (peak value changing means), 8
0 Capacitor switching unit (variable capacitance means).

Claims (6)

[Claims] 1. A voltage generating means for applying a pulse voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining, a capacitance detecting means for detecting a capacitance of the gap, and the electrode Is used as a cathode of the voltage generating means, and a voltage polarity switching means for switching the workpiece to an anode of the voltage generating means, and using the voltage switching generating means based on a detection value of the capacitance detecting means. Control means for switching voltage polarity of the electrode and the workpiece. 2. A variable voltage generating means capable of applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining and changing a voltage value, and a static voltage detecting means for detecting a capacitance of the gap. An electric discharge machining apparatus comprising: a capacitance detection unit; and a control unit that changes a voltage value generated by the variable voltage generation unit based on a detection value of the capacitance detection unit. 3. A voltage generating means for applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining; a capacitance detecting means for detecting a capacitance of the gap; And a peak value changing means for changing a peak value of a current flowing in a gap between the workpiece and the workpiece; and a control for controlling a current flowing in the gap by the peak value changing means based on a detection value of the capacitance detecting means. Means, and an electric discharge machining apparatus comprising: 4. A voltage generating means for applying a pulsed voltage to a gap between an opposing electrode and a workpiece to perform electric discharge machining; a capacitance detecting means for detecting a capacitance of the gap; A variable capacitance means for changing a capacitance value of a gap between the variable capacitance means and the workpiece; and changing a capacitance value of the variable capacitance means based on a detection value of the capacitance detection means. An electric discharge machining device comprising: a control unit. 5. A voltage generating means for performing a discharge machining by applying a pulsed voltage to a gap between an opposing electrode and a workpiece, and an average voltage for determining an average voltage value of the gap between the electrode and the workpiece. Reference means; average voltage control means for controlling the average voltage to be a reference value based on the average voltage reference means; capacitance detection means for detecting capacitance between the electrodes; Control means for changing and controlling the voltage value of the average voltage reference means based on the detection value of the capacity detection means. 6. An electric discharge machining apparatus according to claim 1, wherein said capacitance detecting means is a measuring means for measuring a rise time of a voltage in said gap.