JPH07256514A - Electric discharge machining apparatus - Google Patents

Abstract

PURPOSE:To provide an electric discharge machining apparatus capable of precisely detecting and effectively avoiding a pulse break phenomenon making an electric discharging machining surface worse or increasing the consumption of an electrode to make working accuracy worse or provide a problem or reducing working speed. CONSTITUTION:When an electrode 100 is opposed to a workpiece 101 through insulating working liquid and pulse-like voltage is applied between the electrode 100 and workpiece 101 for electric discharging machining, pulse break produced by the interruption of electric discharge within a desired electric discharge keeping time is detected by a pulse break detecting means 107. The frequency of electric discharge having the pulse break and occupying in the whole electric discharge pulse is calculated by a pulse break frequency calculating means 108 to alter properly working requirements with a working requirement altering means on the basis of the frequency of the electric discharge having the pulse break.

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 an electric discharge machine which can detect a phenomenon of pulse cracking in which electric discharge is interrupted during electric discharge machining and avoid the pulse cracking phenomenon. is there.

[0002]

2. Description of the Related Art FIG. 6 is a waveform diagram showing a voltage waveform and a current waveform of a discharge pulse in a conventional electric discharge machining apparatus, which is characterized in that the discharge duration of the discharge pulse is constant. It is an example of (V) and current waveform (I). By keeping the discharge duration constant, there are advantages such that the electric discharge machined surface can be made uniform and the electrode consumption ratio can be made constant. However, when the machining state becomes unstable due to the machining depth becoming deeper or the machining area changing, the discharge is interrupted even within the discharge duration, a so-called pulse cracking phenomenon (hereinafter , Simply called pulse cracking). When a large number of electric discharge pulses that cause pulse breakage occur, not only the electric discharge machined surface becomes non-uniform, but also electrode consumption increases, machining accuracy deteriorates, and machining speed decreases.

As a device for detecting pulse breakage
There is a method disclosed in Japanese Patent Publication No. 55123. This method is to detect the arc break time generated during the discharge duration and generate an abnormal signal when the preset time is exceeded.

[0004]

However, in the conventional electric discharge machining apparatus as described above, the electrode wear or the non-uniformity of the electric discharge surface, which is a problem in electric discharge machining, is rather than the arc break time generated during the electric discharge time. It depended on whether or not it had a pulse crack. For example, since the electrode consumption is greatest at the moment when the discharge occurs, the more the number of pulse cracks is, the more the electrode is consumed and is not directly related to the arc break time.

FIG. 7 is a waveform diagram showing an example of a waveform at the time of the pulse break phenomenon, and shows an example of the voltage waveform (V) and the current waveform (I) in which the pulse break occurs.
When pulses with short arc break times such as in (c) and (e) occur continuously, it is difficult to detect the arc break time, depending on the set value. A pulse with a long break time is easier to detect. However, even a short arc break time pulse such as (a) to (c) or (e) causes abnormal wear of the electrode similarly to a long arc break time pulse such as (d). In addition, JP-A-3-551
No. 23 discloses nothing about a method for avoiding the pulse cracking phenomenon.

Therefore, in the present invention, in the electric discharge machining, the phenomenon of pulse cracking, which has a problem that the electric discharge machined surface is deteriorated, or the electrode consumption is increased to deteriorate the machining accuracy, or the machining speed is lowered, is accurately performed. An object of the present invention is to provide an electric discharge machine that can be detected and can be effectively avoided.

[0007]

According to a first aspect of the present invention, there is provided an electric discharge machining apparatus in which an electrode and a workpiece are opposed to each other with a machining fluid interposed therebetween, and a pulsed voltage is applied between the electrode and the workpiece. To generate an electric discharge, and electric discharge machining means for processing the workpiece with the electric discharge energy, and a pulse crack for detecting that the electric discharge is interrupted within a desired electric discharge duration for each electric discharge and a pulse crack occurs. It is provided with a detecting means and a pulse breakage frequency calculating means for calculating the frequency of the discharge having the pulse breakage in the entire discharge pulse.

According to a second aspect of the present invention, there is provided an electric discharge machining apparatus, which has the same electric discharge machining means, pulse crack detection means, and pulse crack frequency calculation means as those of the first aspect, and in addition, the pulse crack frequency calculation means. The processing condition changing means for changing the processing condition according to the frequency of the generated discharge pulse is provided.

According to a third aspect of the present invention, there is provided an electric discharge machining apparatus, which has the same electric discharge machining means, pulse breakage detecting means, and pulse breakage frequency calculating means as those of the first and second preferred embodiments.
The apparatus further comprises pulse crack frequency display means for displaying the pulse crack frequency calculated by the pulse crack frequency calculation means.

[0010]

In the electric discharge machining apparatus of the first aspect of the present invention, the electric discharge machining is performed by making the electrode and the workpiece face each other with the machining liquid interposed therebetween and applying a pulsed voltage between the electrode and the workpiece. At this time, it is to detect the occurrence of pulse breakage due to interruption of discharge within a desired discharge duration for each discharge, and to calculate the frequency of this pulse-breakage discharge in the entire discharge pulse. The cracking phenomenon can be detected accurately.

In the electric discharge machining apparatus according to the second aspect of the present invention, when electric discharge machining is performed, it is checked whether the electric discharge is interrupted during the electric discharge duration, and the frequency is calculated,
Since the machining conditions are appropriately changed on the basis of this, the phenomenon of pulse cracking can be detected accurately, and moreover, electrical discharge machining can be performed by switching to machining conditions that do not cause pulse cracking.

In the electric discharge machining apparatus of the third aspect of the present invention, when electric discharge machining is performed, it is checked whether the electric discharge is interrupted during the electric discharge duration, and the frequency thereof is calculated and displayed. The phenomenon can be detected accurately, and moreover, the fact that a pulse crack has occurred can be notified to the operator or the like.

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram showing an overall configuration diagram of an electric discharge machining apparatus which is an embodiment of the present invention, and shows a block diagram including pulse breakage detecting means. In the figure, 100 is an electrode, 101 is a workpiece to be processed, 102 is a DC power supply, 103 is a switching element such as a transistor, 104 is a resistor, 10
Reference numeral 5 is a discharge detecting means for determining whether or not a discharge is generated between the electrode 100 and the workpiece 101, 106 is an oscillator, and 107 is a pulse crack for detecting that the discharge is interrupted during the set discharge duration. Detecting means, 108 is a pulse cracking frequency calculating means for calculating the frequency of discharge pulses causing pulse cracking, 109 is a numerical control (NC) means, 112 is a pulse cracking frequency displaying means for displaying the frequency of pulse cracking, and 130 is a machining fluid switch. It is a means. Pulse break frequency calculation means 108
Is used to control the working fluid switching means 130. The signal of the pulse breakage frequency calculating means 108 may be sent to the numerical control means 109 once, and the machining liquid switching means 130 may be controlled by the signal of the numerical control means 109.

FIG. 2 is a circuit diagram showing a pulse breakage detecting means of an electric discharge machine which is an embodiment of the present invention, and is a detailed view of the pulse breakage detecting means. In the figure, 1 and 2 are JK flip-flops, 3 are NOT gates, and 4 are NANs.
D gates and 13 are respective logic gates of AND gates.

FIG. 3 is a timing chart showing the timing of each signal in FIG. 2, and is a waveform diagram of the voltage between contacts and a waveform diagram of each part in FIG. In the figure, the signal DPBL is the electrode 1
00 and the workpiece 101, a pulse-like signal that becomes “L” level at the moment when a voltage is applied between them, a signal CTML becomes a “L” level signal during discharging, and a signal TCPH represents a voltage between the electrodes. Is a pulse-like signal which becomes "H" level at the moment when the application of the voltage is stopped. The signal CTQH is a signal which becomes "L" level by the signal DPBL at the moment when the voltage is applied between the electrodes, and the JK flip-flop 1 is reset at the same time when the discharge starts, becomes "H" level, and then the discharge Is terminated, the discharge rest time is terminated, and the voltage is applied between the electrodes next time. The signal CTSH is a signal obtained by passing the signal CTQH and the signal CTRL through the NAND gate 4. The signal CTWH is a signal which becomes “H” level when the discharge is interrupted during the discharge duration, and this signal CTWH becomes “H” level when the signal CTSH becomes “L” level during the discharge duration. .

Therefore, if the signal CTWH is at the "H" level at the end of the discharge duration, the discharge is a pulse-split discharge pulse, while if at the "L" level, the discharge is not pulse-split. It shows that it is a pulse. The signal TCPH is a signal which becomes "L" level at the end of the discharge duration, and the signal CTWH is judged at this timing.

FIG. 4 is a circuit diagram showing a pulse breakage frequency calculation means and a pulse breakage frequency display means of the electric discharge machine which is an embodiment of the present invention. In the figure, the same reference numerals and symbols as those in FIGS. 1 and 2 denote the same or corresponding components as those in FIGS. In the figure, 13 is an AND gate,
14 is a first counter for counting all discharge pulses, 1
Reference numeral 5 is a second counter for counting the discharge pulses having pulse breaks, 16 is a latch circuit for latching the count number of the second counter 15 at the timing when the first counter 14 reaches the set count value, and 17 is a digital signal. A D / A converter for converting into an analog signal, a delay circuit 18 for delaying and transmitting the signal for a predetermined time, and a voltmeter 113.

Next, the operations of the pulse breakage frequency calculation means and the pulse breakage frequency display means will be described. In the pulse breakage detecting means 107 of the electric discharge machining apparatus of this embodiment, the signal TCPH is a pulse signal which becomes the "H" level momentarily at the end of the discharge duration as described above, and the signal CTWH is checked at this timing. , It is determined whether or not the discharge pulse is broken. Therefore, the signal TCPH represents the total number of discharge pulses, and the signal passing through the AND gate 13 represents the number of discharge pulses with pulse breakage. Therefore, when the first counter 14 reaches a certain set value N, the count number of the second counter 15 is latched by the latch circuit 16, and this is counted by the pulse breakage frequency display means 1.
Displayed by 12. When the first counter 14 reaches the set value N, the reset signal passes through the delay circuit 18
The counter 14 and the second counter 15 are reset and the count is reset.

In the detection of the pulse crack in the electric discharge machining apparatus of this embodiment, the number of the discharge pulses having the pulse crack is calculated and displayed. On the other hand, it is conceivable to calculate and display the discharge time with pulse breakage as disclosed in Japanese Patent Application Laid-Open No. 3-55123 described in the conventional example. FIG. 5 shows means for automatically avoiding the pulse crack phenomenon by changing the processing conditions for the outputs of these pulse crack detecting means. FIG. 5 is a circuit diagram showing a machining condition changing means for changing the machining condition according to the frequency of the electric discharge pulse having a pulse crack in the electric discharge machine which is an embodiment of the present invention. In the figure, 19 is a first magnitude comparator that compares the count number of the latch circuit 16 with a first set value, and 20 is a second magnitude comparator that also compares the count number of the latch circuit 16 with a second set value. It is a comparator. The set value is smaller in the first magnitude comparator 19 than in the second magnitude comparator 20. Reference numeral 114 is a processing condition changing means for changing the processing condition.

Next, the operation of the processing condition changing means will be described. The signals of the latch circuit 16 are compared with the respective set values by the first magnitude comparator 19 and the second magnitude comparator 20, and the output of judgment of magnitude is output. Further, the signal of the latch circuit 16 is directly fed to the numerical control means 1
It is also possible to read the data in 09 and perform calculation processing. For example, the servo voltage is increased when the count number of the discharge pulse having the pulse split exceeds the setting value of the first magnitude comparator 19, and the voltage applied between the electrodes when the count value of the discharging pulse exceeds the setting value of the second magnitude comparator 20. Control to raise. If the frequency of pulse breakage is relatively low, the machining state can be recovered by increasing the servo voltage. However, if the frequency is high, it is difficult to recover by changing the servo voltage, and it is possible to increase the applied voltage. It is effective. It is also possible to provide more magnitude comparators and finely control the processing conditions. Other machining conditions to be operated include a jump amount and a discharge rest time. It is also effective to stop the processing and warn the operator or the like.

As described above, the electric discharge machining apparatus of this embodiment is
The electrode 100 and the work piece 101 are opposed to each other with an insulating working liquid interposed therebetween, and a pulsed voltage is applied between the electrode 100 and the work piece 101 to generate an electric discharge, and the electric discharge energy causes the work piece 101 to be processed. A well-known electric discharge machining means for machining the electric field, and a pulse breakage detecting means 107 having a circuit configuration shown in FIG. 2 for detecting the occurrence of pulse breaks due to interruption of the electric discharge within a desired discharge duration for each of the electric discharges. FIG. 4 is a diagram for calculating the frequency of the above-mentioned pulse-breaking discharge in the entire discharge pulse.
Pulse break frequency calculation means 108 having the circuit configuration shown in FIG.

That is, the electric discharge machining apparatus of this embodiment is provided with the electrode 1
00 and the work piece 101 face each other with an insulating working liquid interposed therebetween, and when a pulsed voltage is applied between the electrode 100 and the work piece 101 to perform electric discharge machining, a desired discharge is generated for each discharge. It is detected that the discharge is interrupted within the duration and a pulse crack occurs, and the frequency of the pulse broken discharge in the entire discharge pulse is calculated.

Therefore, by obtaining the frequency of pulse cracking, the pulse cracking phenomenon can be detected more accurately than in the conventional case where the pulse cracking is detected by the arc break time. For this reason, the pulse cracking phenomenon can be accurately detected even when pulses with short arc break times occur consecutively.By using this, it is possible to effectively avoid the pulse cracking phenomenon in electrical discharge machining. Is possible.

In particular, as described in the description of FIG. 5 of the present embodiment, if the machining condition changing means 114 for changing the machining condition according to the frequency of the discharge pulse with the pulse crack by the pulse crack frequency calculating means 108 is provided. When performing electric discharge machining, it is possible to check whether the electric discharge is interrupted during the electric discharge duration, calculate the frequency, and appropriately change the machining conditions based on the calculated frequency. That is, for each discharge, by detecting whether or not the discharge is interrupted within the set discharge duration, the pulse broken discharge is detected, the frequency is counted by the counter, and the machining condition is appropriately set according to the frequency. It is something to switch. Therefore, the phenomenon of pulse cracking can be detected accurately, and furthermore, since it is possible to perform electric discharge machining by switching to machining conditions that do not cause pulse cracking, it is possible to maintain a good electric discharge machined surface,
It is possible to reduce electrode consumption and improve processing accuracy. As a result, a good working state can be maintained at all times.

Further, as described in the description of FIG. 4 of the present embodiment, when the pulse breakage frequency display means 112 for displaying the pulse breakage frequency obtained by the pulse breakage frequency calculation means 108 is provided, when electric discharge machining is performed. In addition, it is possible to check whether the discharge is interrupted during the discharge duration, and calculate and display the frequency. Therefore, the phenomenon of pulse cracking can be detected accurately, and moreover, the fact that pulse cracking has occurred can be notified to the operator or the like, so that appropriate measures such as stopping machining and changing machining conditions can be taken as appropriate. As a result, the electric discharge machining surface can be kept good, electrode consumption can be reduced, and machining accuracy can be improved.

[0026]

As described above, the electric discharge machining apparatus according to the first aspect of the present invention is provided with the electric discharge machining means, the pulse breakage detecting means, and the pulse breakage frequency calculating means, and processes the electrode and the workpiece. When facing each other with a liquid interposed and applying a pulsed voltage between the electrode and the work piece, the discharge is interrupted within the desired discharge duration for each discharge and pulse cracking occurs. It is possible to accurately detect the pulse cracking phenomenon by detecting the occurrence of the pulse cracking and calculating the frequency of this pulse cracking discharge in the entire discharge pulse. It is possible to avoid it.

An electric discharge machine according to a second aspect of the present invention comprises an electric discharge machine, a pulse breakage detector, a pulse breakage frequency calculator, and a machining condition changer. It is possible to accurately detect the phenomenon of pulse cracking by checking whether the electric discharge is interrupted, calculate the frequency, and appropriately change the machining conditions based on it. Since electric discharge machining can be performed, it is possible to maintain a good electric discharge machined surface, reduce the degree of electrode wear, and improve machining accuracy.

An electric discharge machine according to a third aspect of the present invention comprises an electric discharge machine means, a pulse crack detecting means, a pulse crack frequency calculating means, and a pulse crack frequency display means, and when the electric discharge machining is performed, the discharge duration is maintained. By checking if the discharge is interrupted during the time and calculating and displaying the frequency, it is possible to accurately detect the pulse cracking phenomenon and to notify the operator etc. that the pulse cracking has occurred. It is possible to appropriately take appropriate measures such as changing the machining conditions, to maintain a good electric discharge machined surface, reduce electrode consumption, and improve machining accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration diagram of an electric discharge machine which is an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a pulse breakage detecting means of an electric discharge machine which is an embodiment of the present invention.

FIG. 3 is a timing chart showing the timing of each signal in FIG.

FIG. 4 is a circuit diagram showing a pulse breakage frequency calculation means and a pulse breakage frequency display means of an electric discharge machine which is an embodiment of the present invention.

FIG. 5 is a circuit diagram showing a machining condition changing means for changing the machining condition according to the frequency of the electric discharge pulse having a pulse crack in the electric discharge machine which is an embodiment of the present invention.

FIG. 6 is a waveform diagram showing a voltage waveform and a current waveform of a discharge pulse in a conventional electric discharge machine.

FIG. 7 is a waveform diagram showing an example of a pulse split waveform.

[Explanation of symbols]

 1 JK Flip-Flop 2 JK Flip-Flop 3 NOT Gate 4 NAND Gate 13 AND Gate 14 Counter 15 Counter 16 Latch Circuit 17 D / A Converter 18 Delay Circuit 19 Magnitude Comparator 20 Magnitude Comparator 100 Electrode 101 Workpiece 105 Discharge Detection Means 106 Oscillator 107 Pulse crack detection means 108 Pulse crack frequency calculation means 109 Numerical control means 112 Pulse crack frequency display means 113 Voltmeter 114 Processing condition changing means

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[Procedure amendment]

[Submission date] February 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a block diagram showing an overall configuration diagram of an electric discharge machining apparatus which is an embodiment of the present invention, and shows a block diagram including pulse breakage detecting means. In the figure, 100 is an electrode, 101 is a workpiece to be processed, 102 is a DC power supply, 103 is a switching element such as a transistor, 104 is a resistor, 10
Reference numeral 5 is a discharge detecting means for determining whether or not a discharge is generated between the electrode 100 and the workpiece 101, 106 is an oscillator, and 107 is a pulse crack for detecting that the discharge is interrupted during the set discharge duration. Detecting means, 108 is a pulse cracking frequency calculating means for calculating the frequency of discharge pulses causing pulse cracking, 109 is a numerical control (NC) means, 112 is a pulse cracking frequency displaying means for displaying the frequency of pulse cracking, and 130 is a machining fluid switch. It is a means. Pulse break frequency calculation means 108
Is used to control the working fluid switching means 130. or,
By the working fluid switching means 130, the normal working fluid and pulse division
Change the working fluid that does not easily cause this. In addition, the signal of the pulse breakage frequency calculation means 108 is changed to the numerical control means 109.
Alternatively, the machining fluid switching means 130 may be controlled by a signal from the numerical control means 109.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Akihiro Goto Inventor Akihiro 5-14 Yada Minami 5-chome, Higashi-ku, Nagoya, Aichi Mitsubishi Electric Corporation Nagoya Works (72) Inventor Hidetoshi Kawazu 5-chome Yada Minami, Higashi-ku, Aichi Prefecture No. 1-14 Mitsubishi Electric Corporation Nagoya Works

Claims (3)

[Claims] 1. An electric discharge in which an electrode and a workpiece are opposed to each other with a machining liquid interposed therebetween, a pulsed voltage is applied between the electrode and the workpiece to cause discharge, and the workpiece is processed by the discharge energy. Machining means, pulse breakage detection means for detecting the occurrence of pulse breakage by interrupting the discharge within a desired discharge duration for each discharge, and calculating the frequency of the pulse breakage discharge in the entire discharge pulse And an electric discharge machining device for calculating a pulse breakage frequency. 2. An electrode and a work piece are opposed to each other with a working fluid interposed therebetween, a pulsed voltage is applied between the electrode and the work piece to generate an electric discharge, and the work piece is processed with the discharge energy. Electrical discharge machining means, a pulse crack detection means for detecting the occurrence of pulse cracking due to interruption of discharge within a desired discharge duration for each of the discharges, and the frequency at which the pulse cracked discharge occupies the entire discharge pulse An electric discharge machining apparatus comprising: a pulse cracking frequency calculating means for calculating the above; and a machining condition changing means for changing the machining condition according to the frequency of the discharge pulse pulse-cracked by the pulse cracking frequency calculating means. 3. An electrode and a work piece are opposed to each other with a working fluid interposed therebetween, a pulsed voltage is applied between the electrode and the work piece to generate electric discharge, and the work piece is processed with the discharge energy. Electrical discharge machining means, a pulse crack detection means for detecting the occurrence of pulse cracking due to interruption of discharge within a desired discharge duration for each of the discharges, and the frequency at which the pulse cracked discharge occupies the entire discharge pulse An electric discharge machining apparatus comprising: a pulse crack frequency calculation means for calculating the pulse crack frequency and a pulse crack frequency display means for displaying the pulse crack frequency obtained by the pulse crack frequency calculation means.