JPH07156019A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To prevent convergence of discharge and a flaw in an electrode because of a short-circuit current flowing in the case of short-circuit between the electrode and a material to be processed via machined chips, and also to improve a machining speed in electric discharge machining. CONSTITUTION:An electric discharge machining device is provided with a short- circuit detecting circuit 306 detecting short-circuit between an electrode 302 and a material to be processed 303 and a pulse cut circuit 318, and the pulse cut circuit 318 outputs a signal for turning off a switching element 308 so as to stop impression of the next processing pulse if the short-circuit detecting circuit 306 detects short-circuit during a resting duration of the processing pulse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machine, and more particularly to early elimination of a short circuit current flowing when a short circuit occurs between an electrode and a workpiece.

[0002]

2. Description of the Related Art In conventional electric discharge machining, a short-circuit current flowing when an electrode and a workpiece are short-circuited is considered to be a reactive current that does not contribute to machining, and no special measures have been taken at present. It was This is because there are many unclear points about the influence of the short-circuit current, and it was not considered to be so harmful even if no measures were taken. However, recent research has revealed the following three things. First, the short circuit current does not itself create arc marks or stains on the work piece, but it does. Secondly, when a short circuit occurs, the electrodes are easily scratched or abnormally worn. Third,
Once a short circuit occurs, it tends to continue for a long time. If a short circuit occurs during electrical discharge machining, several tens of μs to several 100 μs
It continues for as long as s. Generally, an electric discharge machine performs a servo that controls the distance between the electrodes by the voltage between the electrodes. Therefore, when a short circuit occurs, the electrode and the workpiece move in the direction of moving away from each other, and after a time of about several tens of μs, The calculation should be sufficient to eliminate the short, but it is not.

It has been clarified that these problems are caused by a short-circuit current that flows through machining waste at the time of short-circuit. FIG. 7 shows a state in which a short-circuit current is flowing through the processing waste as viewed from above. When the short-circuit current flows, a magnetic field is generated in the direction of the arrow in the figure, and the magnetic field causes the processing chips to be attracted toward the center. Therefore, when a short circuit occurs, the processing wastes are collected, and the short circuit continues for a long time, which causes discharge concentration and electrode damage.

As one method for solving such a problem, Japanese Patent Application Laid-Open No. 53-105795 and US Pat.
As in 51969 and 3609281, methods of applying a high current pulse have been proposed. These methods are methods for melting a metal bridge formed when an electrode and a workpiece are melted by electric discharge with a high current. However, the short-circuit state continues not because of the metal bridge, but because of processing scraps collected by the electromagnetic force generated by the short-circuit current (hereinafter referred to as short-circuit bridge). These methods do not consider that the short-circuit phenomenon that occurs during electric discharge machining occurs due to the collection of machining chips, and therefore is a fundamental measure against the short-circuit current that causes the short-circuit state to continue. Not not.

As described above, the cause of continuing the short-circuit state is due to the processing wastes collected by the electromagnetic force generated by the short-circuit current. Therefore, in order to solve the above problems, it is effective to stop the current at the time of short circuit. This is because by stopping the current at the time of short circuit, the concentration of processing chips can be prevented. As a method for measuring the decrease in the inter-electrode impedance and stopping the application of the voltage pulse, Japanese Patent Publication No. 59-23937 and Japanese Patent Laid-Open No. 1-131 are disclosed.
There are JP-A-03227 and JP-A-1-257514, but it is assumed that these methods detect a state in which the gap between electrodes is lowered, that is, a state in which the gap between the electrodes is contaminated by machining waste or a decomposed product of machining fluid. Therefore, unlike the present invention, the problem of concentration of processing chips due to current at the time of short circuit is not recognized. These methods have a problem that the machining speed is reduced because the pulse application is stopped when the inter-electrode impedance is reduced.

By the way, although it has been described that the concentration of the machining waste can be prevented by stopping the current at the time of the short circuit, once the electrode and the workpiece are short-circuited via the machining waste, the electrode and the workpiece are separated from each other. The surface tension causes a short circuit to some extent. Compared with the case where a short-circuit current is applied, this phenomenon has less problems such as continuous short circuits and scratches on electrodes, but has a problem that the processing speed decreases.

[0007]

As described above, when a short circuit occurs through machining scraps during electric discharge machining and a short-circuit current flows, a magnetic field is created by the current flowing through the machining scraps, and Receives a force that draws in a direction. Due to this force, processing chips are collected to form a short-circuit bridge, and short-circuiting continues for a long time, which causes discharge concentration and electrode damage.

The present invention has been made to solve this problem, and an object of the present invention is to provide an electric discharge machine capable of eliminating a short-circuit current at an early stage.

[0009]

According to a first aspect of the present invention, there is provided an electric discharge machining apparatus which detects a short circuit between an electrode and a workpiece, and the short circuit detecting means detects a short circuit during a pause of a machining pulse. In this case, a pulse stop means for stopping the application of the next machining pulse is provided.

The electric discharge machining apparatus according to the second aspect of the present invention includes short-circuit detection means for detecting a short circuit between the electrode and the workpiece, and pulse stop for stopping the application of the machining pulse when the short-circuit detection means detects a short circuit. And a short-circuit elimination pulse applying means for applying a short-circuit elimination pulse between the electrode and the workpiece when the short-circuit continues for a predetermined period of time.

The electric discharge machining apparatus according to the third aspect of the present invention includes a short circuit detecting means for detecting a short circuit between the electrode and the workpiece, and a pulse stop for stopping the application of the machining pulse when the short circuit detecting means detects a short circuit. Means, short-circuit elimination pulse applying means for applying a short-circuit elimination pulse between the electrode and the workpiece when the short-circuit continues for a predetermined period, and the electrode at the time of pulse application immediately after the short-circuit elimination pulse is applied. And short-circuit elimination frequency measuring means for measuring the frequency at which the short-circuit between the workpiece and the work is eliminated, and the short-circuit elimination frequency measured by the short-circuit elimination frequency measuring means is less than or equal to a set value, the current value of the short-circuit elimination pulse. The pulse changing means for increasing the pulse width or extending the pulse width is provided.

Furthermore, an electric discharge machining apparatus according to a fourth aspect of the present invention comprises short circuit detection means for detecting a short circuit between the electrode and the workpiece.
When the short circuit detection means detects a short circuit, pulse stopping means for stopping the application of the machining pulse, and when the short circuit continues for a predetermined period, a short circuit elimination pulse corresponding to the machining pulse is applied to the electrode and the workpiece. It is configured to include a short-circuit elimination pulse applying means applied between.

[0013]

In the pulse stopping means according to the first aspect of the invention, when the short circuit detecting means detects a short circuit during the machining pulse down time,
The application of the next machining pulse is stopped to prevent short-circuit current from flowing between the electrodes.

The pulse stopping means according to the second invention is
Immediately stop the application of the machining pulse when the short circuit detection means detects a short circuit while applying the machining pulse, or apply the next machining pulse when the short circuit detection means detects a short circuit during the pause time of the machining pulse. Stop or the short circuit detection means immediately stops the application of the machining pulse when the short circuit is detected during the application of the machining pulse, and the short circuit detection means detects the short circuit during the rest time of the machining pulse. The operation of stopping the application of the machining pulse is performed to prevent the short-circuit current from flowing between the electrodes. Further, the short-circuit elimination pulse applying means removes the short-circuit bridge by applying a predetermined current pulse between the electrodes when the inter-electrode short circuit continues for a predetermined period.
Remove the short circuit. The reason for applying the predetermined current pulse between the electrodes by the short-circuit elimination pulse applying means is after the inter-electrode short circuit has continued for a predetermined period, for the following reason.
That is, immediately after the short circuit occurs, the area of the processing waste in contact with the electrode and the workpiece is large. However, when a short circuit occurs, the electrode and the workpiece are separated by the inter-electrode servo, and the area of the processing waste that contacts the electrode and the workpiece gradually becomes smaller. At that point, the current for removing the short-circuit bridge is passed,
The short circuit bridge can be easily destroyed. If, for example, a current is passed immediately after the occurrence of a short circuit, the area of the processing waste that is in contact with the electrode and the work piece is large, that is, the shorting bridge cannot be removed because the shorting bridge is thick. Will result in concentration. Therefore, the operation of waiting for the application of current is performed until the short-circuit bridge becomes thin.

The pulse stopping means according to the third invention is
Immediately stop the application of the machining pulse when the short circuit detection means detects a short circuit while applying the machining pulse, or apply the next machining pulse when the short circuit detection means detects a short circuit during the pause time of the machining pulse. Stop or the short circuit detection means immediately stops the application of the machining pulse when the short circuit is detected during the application of the machining pulse, and the short circuit detection means detects the short circuit during the rest time of the machining pulse. The operation of stopping the application of the machining pulse is performed to prevent the short-circuit current from flowing between the electrodes. Further, the short-circuit elimination pulse applying means removes the short-circuit bridge by applying a predetermined current pulse between the electrodes when the inter-electrode short circuit continues for a predetermined period.
Remove the short circuit. Further, the pulse changing means, when the short circuit cannot be often eliminated by applying the current pulse between the electrodes by the short circuit eliminating pulse applying means, the energy is too small for removing the short circuit bridge. Increase the current value, pulse width, or both.

Still further, in the pulse stopping means according to the fourth invention, when the short circuit detecting means detects a short circuit during the application of the machining pulse, the machining pulse application is immediately stopped, or the short circuit detecting means detects the machining pulse. When a short circuit is detected during the pause time, the application of the next machining pulse is stopped, or when the short circuit detection means detects a short circuit during the application of the machining pulse, the machining pulse is immediately stopped and the short circuit is detected. When the means detects a short circuit during the resting period of the machining pulse, it performs an operation of stopping the application of the next machining pulse to prevent a short circuit current from flowing between the electrodes. Further, the short-circuit elimination pulse applying means, when the inter-electrode short circuit continues for a predetermined period,
A short circuit bridge is eliminated by applying a current pulse according to the machining pulse between the electrodes to eliminate the short circuit bridge.

[0017]

【Example】

Example 1. Embodiment 1 of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a configuration diagram showing a first embodiment of the present invention. In the figure, 301 is a DC power source, 302 is an electrode, 303 is a workpiece, 306 is L when the gap between the electrodes is short-circuited, and other than that. Short circuit detection circuit that outputs H signal,
307 is a pulse generator, 308 and 309 are switching elements, 310 and 311 are diodes, 312 and 313.
Is a resistor, 314, 315, 316, 317 is a one-shot multivibrator that generates a pulse of H by a falling trigger, and 318 is a period L of (on time + pause time) when a pulse of H is input to the input. A pulse cut circuit that outputs a signal, 319 and 321 are AND circuits, and 320 is an N circuit.
It is an OT circuit.

FIG. 2 is a timing chart showing the operation of FIG. 1 and voltage / current waveforms between the electrodes. In the figure, A is the output of the pulse generator 307, B is the voltage between the electrode 302 and the work piece 303, C is the same current, and D is the short circuit detection circuit 3.
06 output, E is one-shot multi-vibrator 31
4 output, F is one-shot multi-vibrator 315
, G is the output of the one-shot multivibrator 317, and H is the output of the pulse cut circuit 318.

Next, the operation will be described. The pulse generator 307 is a circuit that outputs a pulse signal for driving the switching element 308.
08 is turned on to apply a voltage between the electrode 302 and the work piece 303, and when L is set, the switching element 308 is turned off and no voltage is applied between the electrode 302 and the work piece 303. The short circuit detection circuit 306 includes the electrode 302 and the workpiece 30.
A short circuit of No. 3 is detected, and an L signal is output when there is a short circuit and a H signal is output when there is no short circuit. The configuration of the short-circuit detection circuit can be configured by, for example, a comparator that measures the voltage of the electrode 302 and the work piece 303 and uses the voltage of 0 V or a value close thereto as a threshold value. When the pulse generator 307 becomes L and the rest time is reached, the one-shot multivibrator 31
4 temporarily becomes H, and then the one-shot multivibrators 315 and 316 generate a pulse.

When the switching element 309 is turned on by the output of the one-shot multivibrator 315 and a voltage is applied between the idle poles and there is no short circuit between the poles, the output of the short circuit detection circuit 306 becomes H. , L when there is a short circuit between the electrodes. At that time, the output of the short-circuit detection circuit is determined at the timing of the one-shot multivibrator 317, and if there is a short circuit between the electrodes, the AND circuit 319.
The pulse is input to the pulse cut circuit 318 as the output of, and the application of the next voltage pulse is stopped. The output of the multivibrator 314, 315, 316, and 317 is set to be in a rest state, and the length of the pulse output from the multivibrator 315 is longer than the output length of the multivibrator 316. It is set.

Example 2. FIG. 3 is a configuration diagram showing a second embodiment of the present invention. In the figure, 401 is a DC power source, 402 is an electrode, 403 is a workpiece, 406 is L when the gap between the electrodes is short-circuited, and other than that. Short circuit detection circuit that outputs H signal,
407 is a pulse generator, 426, 427, 428 are switching elements, 429, 430, 431 are diodes, 432, 433, 434 are resistors, 414, 41.
5, 416, 417, and 423 are one-shot multivibrators that generate H pulse by a falling trigger, 4
Reference numeral 18 denotes a pulse cut circuit that outputs a period L of (ON time + pause time) when an H pulse is input to the input.
Reference numerals 19 and 421 are AND circuits, 420 and 425 are NOT circuits, 424 is an OR circuit, and 422 is a counter.

FIG. 4 shows the electrode 402 and the work piece 403 of FIG.
2 is a waveform of voltage and current between the two. In the figure, L is a voltage waveform between electrodes, and M is a current waveform.

Next, the operation will be described. The pulse generator 407 is a circuit that outputs a pulse signal for driving the switching element 426.
26 is turned on and a voltage is applied between the electrode 402 and the work piece 403, and when L, the switching element 426 is turned off and no voltage is applied between the electrode 402 and the work piece 403. The short circuit detection circuit 406 includes the electrode 402 and the workpiece 40.
A short circuit of No. 3 is detected, and an L signal is output when there is a short circuit and a H signal is output when there is no short circuit. The configuration of the short-circuit detection circuit can be configured by, for example, a comparator that measures the voltage of the electrode 402 and the workpiece 403 and uses the voltage of 0 V or a value close to it as a threshold value. When the pulse generator 407 becomes L and the rest time is reached, the one-shot multivibrator 41
4 temporarily becomes H, and then the one-shot multivibrators 415 and 416 generate pulses.

When the switching element 427 is turned on by the output of the one-shot multivibrator 415 and a voltage is applied between the idle poles and there is no short-circuit between the poles, the output of the short-circuit detection circuit 406 becomes H. , L when there is a short circuit between the electrodes. At that time, the output of the short circuit detection circuit is determined at the timing of the one-shot multivibrator 417, and if there is a short circuit between electrodes, the AND circuit 419
The pulse is input to the pulse cut circuit 418 as the output of, and the application of the next voltage pulse is stopped. The output of the multi-vibrators 414, 415, 416, and 417 is set to be in a rest state, and the length of the pulse output from the multi-vibrator 415 is longer than the output length of the multi-vibrator 416. It is set.

When the gap between the electrodes is short-circuited and the pulse cut circuit 418 operates, the counter 422 counts up. When the gap between the electrodes is not short-circuited and the pulse cut circuit 418 does not operate, the counter 422 is reset. Counter 42
When 2 counts the set value, that is, when the number of pulses corresponding to the set value is continuously short-circuited, the counter 422
Outputs a pulse of H as a carry and simultaneously resets the counter. The one-shot multi-vibrator 423 outputs a pulse by the pulse of this carry and turns on the switching element 428. As a result, M in FIG.
A current pulse for removing a predetermined short-circuit bridge flows between the electrodes as shown in FIG.

Example 3. FIG. 5 is a configuration diagram showing a third embodiment of the present invention. In the figure, 501 is a DC power source, 502 is an electrode, 503 is a work piece, 506 is L when the gap between the electrodes is short-circuited, and other than that. Short circuit detection circuit that outputs H signal,
507 is a pulse generator, 526, 527, 528 are switching elements, 529, 530, 531 are diodes, 532, 533, 534 are resistors, 514, 51.
5, 516 and 517 are one-shot multivibrators that generate H pulse by falling trigger, and 518 is a pulse cut circuit that outputs a period L of (ON time + rest time) when H pulse is input to the input. 519, 5
Reference numerals 21, 538 are AND circuits, 520, 525 are NOT circuits, 524 is an OR circuit, 522 is a counter, 523 is a variable one-shot multivibrator whose pulse width can be changed by the output of the pulse width selection circuit 37, 535.
Is a gate circuit that outputs H to the AND circuit 538 side during the first pause time after the counter 522 outputs a carry, and 536 is a short circuit elimination frequency measurement that measures the frequency with which the short circuit is eliminated after the counter outputs a carry. Device, 53
A pulse width selection circuit 7 selects a pulse width of the variable one-shot multivibrator 523.

Next, the operation will be described. The pulse generator 507 is a circuit that outputs a pulse signal for driving the switching element 526.
26 is turned on and a voltage is applied between the electrode 502 and the work piece 503, and when L, the switching element 526 is turned off and no voltage is applied between the electrode 502 and the work piece 503. The short circuit detection circuit 506 includes the electrode 502 and the workpiece 50.
A short circuit of No. 3 is detected, and an L signal is output when there is a short circuit and a H signal is output when there is no short circuit. The configuration of the short-circuit detection circuit can be configured by, for example, a comparator that measures the voltage of the electrode 502 and the workpiece 503 and uses the voltage of 0 V or a value close to it as a threshold value. When the pulse generator 507 becomes L and the rest time is reached, the one-shot multivibrator 51
4 temporarily becomes H, and then the one-shot multivibrators 515 and 516 generate pulses.

When the switching element 527 is turned on by the output of the one-shot multivibrator 515 and a voltage is applied between the idle poles, and there is no short circuit between the poles, the output of the short circuit detection circuit 506 becomes H. , L when there is a short circuit between the electrodes. At that time, the output of the short-circuit detection circuit is determined at the timing of the one-shot multivibrator 517, and if there is an inter-electrode short circuit, the AND circuit 519
The pulse is input to the pulse cut circuit 518 as the output of, and the application of the next voltage pulse is stopped. Note that the output of the multivibrator 514, 515, 516, 517 is set to be in a rest state, and the length of the pulse output by the multivibrator 515 is longer than the output length of the multivibrator 516. It is set.

When the pulse cut circuit 518 operates due to the short circuit between the electrodes, the counter 522 counts up, and when the pulse cut circuit 518 does not operate due to the short circuit between the electrodes, the counter 522 is reset. Counter 52
When 2 counts the set value, that is, when the number of pulses corresponding to the set value is continuously short-circuited, the counter 522
Outputs a pulse of H as a carry and simultaneously resets the counter. The one-shot multivibrator 523 outputs a pulse by the pulse of this carry and turns on the switching element 528. As a result, a current pulse for removing a predetermined short-circuit bridge flows between the electrodes.

When the counter 522 outputs a carry and the switching element 528 is turned on and a current pulse flows,
The gate circuit 535 outputs H during the first pause time after the counter 522 outputs carry, and the AND circuit 51
The output of 9 can pass through the AND circuit 538.
Then, the short-circuit elimination frequency measuring device 536 measures the total number of current pulses and the number of short-circuits of the pulses after the current pulse to measure the short-circuit elimination frequency. When the short circuit elimination frequency is lower than the set value, the pulse width selection circuit 537 extends the width of the current pulse.

Although the pulse width of the current pulse is changed in the third embodiment, the current value may be changed largely or both of them may be changed.

Example 4. FIG. 6 is a configuration diagram showing a fourth embodiment of the present invention. In the figure, 601 is a DC power source, 602 is an electrode, 603 is a work piece, 606 is L when the gap between the electrodes is short-circuited, and otherwise. Short circuit detection circuit that outputs H signal,
607 is a pulse generator, 614, 615, 616, 6
Reference numerals 17 and 623 are one-shot multivibrators that generate a pulse of H with a falling trigger, and 618 is H to the input.
Pulse cut circuit that outputs a period L of (ON time + pause time) when a pulse of 6 is input, 619 and 621 are AND circuits, 620 and 625 are NOT circuits, and 624 is O.
R circuit, 622 is a counter, 631 to 637 are diodes, 638 to 644 are resistors, 645 to 651 are switching elements, 661 and 662 are changeover switches, 66
Reference numeral 3 denotes a machining current setting device that switches the changeover switches 661 and 662 in conjunction with each other.

Next, the operation will be described. The pulse generator 607 is a circuit that outputs a pulse signal for driving the switching elements 645, 646, 647, and when the voltage is H, the switching elements 645, 646, 647 are turned on and a voltage is applied between the electrode 602 and the workpiece 603. When applied and L, the switching elements 645, 646, 647 are turned off, and no voltage is applied between the electrode 602 and the workpiece 603. However, the switching elements 645, 646, 64
Even if 7 is turned on, current flows only to the switching element whose changeover switch 661 is turned on by the signal from the machining current setting device 633. This changeover switch 6
The machining current is determined by 61. Short circuit detection circuit 606
Detects a short circuit between the electrode 602 and the workpiece 603, and outputs a signal of L when there is a short circuit and H when there is no short circuit. The configuration of the short-circuit detection circuit can be configured by, for example, a comparator that measures the voltage of the electrode 602 and the workpiece 603 and uses the voltage of 0 V or a value close to it as a threshold value.

When the pulse generator 607 becomes L and the rest time is reached, the one-shot multivibrator 614 temporarily becomes H, and then the one-shot multivibrators 615 and 616 generate pulses. When the switching element 648 is turned on by the output of the one-shot multivibrator 615 and a voltage is applied between the idle poles, and the gap between the gaps is not short-circuited, the output of the short-circuit detection circuit 606 becomes H and the gap between the gaps becomes high. When is short-circuited, it becomes L. At that time, the output of the short-circuit detection circuit is determined at the timing of the one-shot multivibrator 617, and if there is a short circuit between electrodes, a pulse is input to the pulse cut circuit 618 as the output of the AND circuit 619, and the next voltage pulse is applied. Is stopped. In addition, the multi-vibrator 614, 615,
It is set that all the outputs of 616 and 617 are in the idle state, and the length of the pulse output from the multivibrator 615 is set to be equal to or longer than the output length of the multivibrator 616.

When the gap between the electrodes is short-circuited and the pulse cut circuit 618 operates, the counter 622 counts up. When the gap between the electrodes is not short-circuited and the pulse cut circuit 618 does not operate, the counter 622 is reset. Counter 62
When 2 counts the set value, that is, when the number of pulses corresponding to the set value is continuously short-circuited, the counter 622
Outputs a pulse of H as a carry and simultaneously resets the counter. The one-shot multi-vibrator 623 outputs a pulse in response to the carry pulse to turn on the switching elements 649, 650, 651. However, even if the switching elements 649, 650, 651 are turned on, the current flows only to the switching element whose changeover switch 662 is turned on by the signal of the machining current setting device 633. The changeover switch 662 determines the current value of the current pulse. Changeover switch 6
61 and 662 are interlocked, and the current value of the current pulse for removing the short-circuit bridge is set according to the machining current value.

[0036]

As described above, according to the first aspect of the invention, short-circuit detecting means for detecting a short circuit between the electrode and the workpiece,
When the short-circuit detection means detects a short-circuit during the resting time of the machining pulse, the short-circuit bridge is formed by the short-circuit current, because the short-circuit current is provided with the pulse stopping means for stopping the application of the next machining pulse. Therefore, it is possible to prevent the phenomenon that the short circuit continues for a long time, the discharge is concentrated, and the electrode is damaged.

According to the second invention, short-circuit detecting means for detecting a short circuit between the electrode and the workpiece, and pulse stopping means for stopping the application of the machining pulse when the short-circuit detecting means detects a short circuit, When the short circuit continues for a predetermined period of time, it is configured to include a short circuit elimination pulse applying means for applying a short circuit elimination pulse between the electrode and the workpiece, so that the short circuit state is quickly eliminated and the machining state is stabilized. Can be kept at

According to the third invention, short-circuit detecting means for detecting a short circuit of the electrode and the workpiece, and pulse stopping means for stopping the application of the machining pulse when the short-circuit detecting means detects a short circuit, When the short circuit continues for a predetermined period, short-circuit elimination pulse applying means for applying a short-circuit elimination pulse between the electrode and the workpiece, and the electrode and the workpiece at the time of pulse application immediately after the short-circuit elimination pulse is applied. If the short circuit elimination frequency measuring means for measuring the frequency at which the short circuit is eliminated, and the short circuit elimination frequency measured by the short circuit elimination frequency measuring means is less than or equal to a set value, is the current value of the short circuit elimination pulse increased? Alternatively, since the pulse changing means for extending the pulse width is provided, it is possible to eliminate the short-circuited state more quickly than in the second aspect of the invention and keep the machining state stable.

Further, according to the fourth invention, short-circuit detecting means for detecting a short circuit of the electrode and the workpiece, and pulse stopping means for stopping the application of the machining pulse when the short-circuit detecting means detects a short circuit. When the short circuit continues for a predetermined period, it is configured to include a short circuit elimination pulse applying means for applying a short circuit elimination pulse corresponding to the machining pulse between the electrode and the workpiece, It is possible to quickly eliminate the short circuit condition under suitable conditions.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a timing chart and a voltage / current waveform diagram between electrodes for explaining the operation of the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a voltage and current waveform diagram for explaining the operation of the second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a third embodiment of the present invention.

FIG. 6 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a short circuit state.

[Explanation of symbols]

301 power supply 302 electrode 303 work piece 308 switching element 309 switching element 310 diode 311 diode 306 short-circuit detector 307 pulse generator 314, 315, 316, 317 one-shot multivibrator 318 pulse-cut circuit 422 counter 536 short-circuit elimination frequency measuring circuit 537 Pulse width selection circuit 661, 662 Changeover switch 663 Processing current setting device

Claims (4)

[Claims] 1. An electric discharge in which an electrode and a workpiece are opposed to each other with a machining liquid interposed therebetween, a machining pulse is applied between the electrode and the workpiece to generate an electric discharge, and the electric energy is used to machine the workpiece. In the processing apparatus, short-circuit detection means for detecting a short circuit between the electrode and the workpiece, and pulse stop means for stopping the application of the next processing pulse when the short-circuit detection means detects a short circuit during the pause time of the processing pulse. An electric discharge machine equipped with. 2. An electric discharge in which an electrode and a workpiece are opposed to each other with a machining liquid interposed therebetween, a machining pulse is applied between the electrode and the workpiece to generate an electric discharge, and the electric energy is used to machine the workpiece. In the processing apparatus, short-circuit detection means for detecting a short circuit between the electrode and the workpiece, pulse stop means for stopping the application of the processing pulse when the short-circuit detection means detects a short circuit, and the short circuit continues for a predetermined period. In this case, the electric discharge machining apparatus is provided with a short circuit elimination pulse applying means for applying a short circuit elimination pulse between the electrode and the workpiece. 3. An electric discharge in which an electrode and a workpiece are opposed to each other with a machining liquid interposed therebetween, a machining pulse is applied between the electrode and the workpiece to generate an electric discharge, and the electric energy is used to machine the workpiece. In the processing apparatus, short-circuit detection means for detecting a short circuit between the electrode and the workpiece, pulse stop means for stopping the application of the processing pulse when the short-circuit detection means detects a short circuit, and the short circuit continues for a predetermined period. In this case, the short-circuit elimination pulse applying means for applying the short-circuit elimination pulse between the electrode and the workpiece, and the short-circuit between the electrode and the work are eliminated at the pulse application time immediately after the short-circuit elimination pulse is applied. Short-circuit elimination frequency measuring means for measuring the frequency, when the short-circuit elimination frequency measured by the short-circuit elimination frequency measuring means is less than a set value,
An electric discharge machine comprising pulse changing means for increasing the current value of the short-circuit elimination pulse or extending the pulse width. 4. An electric discharge in which an electrode and a workpiece are opposed to each other with a machining liquid interposed therebetween, a machining pulse is applied between the electrode and the workpiece to generate an electric discharge, and the electric energy is used to machine the workpiece. In the processing apparatus, short-circuit detection means for detecting a short circuit between the electrode and the workpiece, pulse stop means for stopping the application of the processing pulse when the short-circuit detection means detects a short circuit, and the short circuit continues for a predetermined period. In this case, the electric discharge machining apparatus comprises a short circuit elimination pulse applying means for applying a short circuit elimination pulse corresponding to the machining pulse between the electrode and the workpiece.