JP2587956B2 - Control device for wire electric discharge machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control apparatus for a wire electric discharge machine that generates a discharge between a traveling wire electrode and a workpiece and processes the workpiece with discharge energy. .

[Conventional technology]

2. Description of the Related Art Conventionally, a wire electric discharge machine currently processes a workpiece using a portion in which a wire electrode travels in a vertical direction. The wire electrode is guided by a roller fixed to the main body of the wire electric discharge machine, and is supplied to a wire head having a wire guide.

On the other hand, the table on which the workpiece is mounted moves in the X and Y directions according to the processing status of the workpiece according to instructions from the NC device, and repeats servo movement with the wire electrode supplied to the wire head for processing. Progresses. In other words, not only does the wire head relatively advance in the machining direction during wire electric discharge machining, but also when the electric discharge machining becomes unstable in accordance with the situation of machining chips, etc. Retreat along. Next, the electric discharge machining is performed again. And, after receiving a command from the NC device,
The workpiece moves in the horizontal direction, that is, the X direction and the Y direction, the movements of the two are combined, and the workpiece is subjected to electric discharge machining into a predetermined machining shape by the relative movement of the two.

By the way, in the power supply device for electric discharge machining in a conventional wire electric discharge machine, in order to check the insulation recovery state of a machining fluid in a machining gap between a wire electrode and a workpiece, a waveform of a gap voltage is detected. This is performed according to the level or magnitude of the voltage waveform. That is, in the voltage waveform diagram shown in FIG. 4, when the elapsed time t (μs) is plotted on the horizontal axis,
Waveform (A) shows the no-load voltage V _0, the waveform (B) shows the machining gap voltage V _G applied between the wire electrode and the workpiece, also the waveform (C) shows a discharge current I _W . In the discharge current _IW , the symbol a is the discharge current during normal discharge, and the symbol b is the discharge current during abnormal discharge that does not contribute to electrical discharge machining. If the inter-electrode voltage V _G does not reach the predetermined voltage V _L is an abnormal discharge.

Conventionally, Japanese Patent Application Laid-Open No. 54-156296 discloses a control method of a wire electric discharge machine. The control method of the wire-cut electric discharge machine has a switching element in a charging circuit of a capacitor, utilizing charging and discharging of the capacitor, in a current-carrying gap formed between a wire electrode and a workpiece, Electric cutting is performed intermittently by discharging current, and the charging current of the capacitor is controlled in accordance with the state of the energized machining gap. The state of the energized machining gap is similar to a short circuit or continuous arc state. Even when the state is detected, the current flowing through the energized machining gap does not decrease for a predetermined time, and if the state of the energized machining gap does not return within the predetermined time, the state of the energized machining gap is reduced. This is to reduce the current flowing.

Further, a wire electrode disconnection prevention circuit for wire electric discharge machining for preventing disconnection of a wire electrode in wire electric discharge machining is disclosed in JP-A-61-288930 and JP-A-61-288931. The wire electric discharge machining wire electrode disconnection prevention circuit is configured to reduce a variation in a machining current flowing through at least one of a power supply provided on an upper side and a lower side with respect to a workpiece in order to supply a machining current to the wire electrode. A concentrated discharge detection circuit for detecting whether or not a concentrated discharge state is detected, and a processing average current for detecting whether or not the processing average current is equal to or more than a predetermined value set according to the current capacity of the wire electrode The detection circuit and the signals from both of these detection circuits are input, and the pulse ON / OFF time of the pulse power supply is set when the state in which the concentrated current is in the concentrated discharge state and the state in which the machining average current is equal to or more than the predetermined value continues for a predetermined time or more. And a control circuit for reducing the energy of the arc discharge by controlling, and further detects a short circuit between the wire electrode and the workpiece, and reduces the detection sensitivity of the concentrated discharge detection circuit when the short circuit occurs. Those having a sensitivity correction circuit for.

Furthermore, as a power supply device for electric discharge machining in a wire cut electric discharge machine, that is, a wire electric discharge machine, there is one disclosed in Japanese Utility Model Laid-Open Publication No. 59-8729. The power supply device for wire-cut electric discharge machining disclosed in this publication binarizes a discharge state between both electrodes of a wire electrode and a work, and continuously counts and measures the binarized abnormal discharge state in a predetermined time cycle. When the counted value exceeds the set count value, the machining pulse transistor is turned off in response to the signal of the abnormal discharge phenomenon to temporarily suspend the abnormal discharge, and wait for the state recovery between both electrodes to perform electric discharge machining. Is to be restarted. That is, the electric discharge machining current is temporarily interrupted in response to the detection of the abnormal discharge. If the abnormal discharge occurs, the abnormal discharge is continuously counted, and the machining pulse is not counted until the count value becomes equal to or larger than a preset count value. Transistor is turned on.

[Problems to be solved by the invention]

However, as described above, in order to check the insulation recovery state of the machining fluid in the machining gap between the wire electrode and the workpiece, the waveform of the voltage between the electrodes is detected, and the operation is performed based on the level or magnitude of the voltage waveform. In such a detection method, a discharge current is applied regardless of whether or not residual ions exist in the machining fluid between the electrodes.

However, when residual ions are present in the machining fluid between the wire electrode and the workpiece, the discharge voltage applied between the electrodes does not become a normal discharge, but becomes an abnormal discharge, and therefore, the supplied machining pulse power Is not used as machining energy for electric discharge machining, in other words, part of the discharge energy is wasted as abnormal extraordinary energy that does not contribute to electric discharge machining.

In addition, as the abnormal discharge energy increases, the processing speed of the workpiece further decreases, and abnormal discharge is applied to the workpiece, which causes the finish accuracy of the processed surface of the workpiece to be rough. .

It is clear that the control method of the wire electric discharge machine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 54-156296 has the same problems as described above. Further, the control method of the wire-cut electric discharge machine reduces the electric discharge machining current if the abnormal electric discharge continues for a predetermined time, and allows the original normal electric discharge machining current to flow while monitoring the discharge voltage and waiting for natural recovery. However, even though the current is reduced, the discharge cannot be dispersed and the concentrated discharge persists as long as the current flows, and it takes a long time for the spontaneous recovery to take place. In addition to this, there is an undesired problem of lowering the machining surface accuracy. In addition, since a capacitor is used for measuring the duration of abnormal discharge, it varies depending on the power supply voltage, temperature, and the like, and has problems in accuracy, reproducibility, and the like. Further, since the duration is set by manual operation of the variable resistor, a setting error is large, a setting operation error occurs, and there are problems in accuracy, reproducibility, and the like.

Further, the above-mentioned JP-A-61-288930 and JP-A-61-288930 are disclosed.
No. 2,889,311, the wire electrode disconnection prevention circuit for wire electric discharge machining, similarly to the one described in JP-A-54-156296, the arc discharge energy if the abnormal discharge continues for a predetermined time. The discharge energy is wasted and the electric discharge machining speed has the same problems as described above.

To solve the above problems, a power supply device for electric discharge machining in a wire electric discharge machine disclosed in Japanese Utility Model Application Laid-Open No. 59-8729 has been provided. In the power supply device for electric discharge machining, the electric discharge machining current is completely stopped, the generation of useless discharge energy is eliminated, and the recovery to the normal electric discharge machining state is accelerated, without significantly reducing the machining speed. Since counting is performed using digital signals in a predetermined time cycle, errors in time measurement can be reduced, and there is an effect in further increasing the setting accuracy.

However, in actual machining, abnormal discharge occurs for a long time,
For example, the number of machining pulses, that is, the number of discharge current pulses is 100
Since it occurs for a time corresponding to about 200, the period during which the discharge pulse transistor is turned off is set to be cut off for a relatively long time in order to recover the normal discharge state. As described above, the OFF period of the discharge pulse transistor, that is, the period until the application of the discharge current is set in advance, so that the period in which the residual ion concentration is already reduced and abnormal discharge does not occur is also set to the OFF state. There is a problem that a useless time elapses, which causes a disadvantage that the processing efficiency is reduced.

An object of the present invention is to solve the above-described problem, and to determine whether or not abnormal discharge occurs when a discharge current is supplied between a wire electrode and a workpiece, by determining an ion concentration present in a machining fluid. As soon as possible, a discharge current is supplied as soon as the gap state where abnormal discharge does not occur is detected. Therefore, the residual ion concentration of the machining fluid in the machining gap is positively detected. Immediately detect the point at which the residual ion concentration of the machining fluid falls below a predetermined ion concentration, shorten the pulse pause time as much as possible, improve the machining speed for the workpiece, and eliminate abnormal discharge conditions. To provide a control device for a wire electric discharge machine capable of finishing a machined surface of a workpiece with high precision.

[Means for solving the problem]

The present invention is configured as follows to achieve the above object. That is, the present invention provides a pulsed spike voltage by a detection pulse having a width sufficiently shorter than a processing pulse width for checking a residual ion concentration in a processing liquid existing in a processing gap between a wire electrode and a workpiece. It is applied until the insulation of the machining fluid is restored to the machining gap continuously at regular intervals set in advance during the pause time, and the spike voltage by the detection pulse is a predetermined value indicating the insulation restoration of the machining fluid. In response to the voltage being equal to or higher than the set value, at the timing of issuing the next detection pulse, the processing pulse rise time and the processing pulse pause time width are determined based on the constant time interval of the detection pulse. A control of a wire electric discharge machine, wherein a discharge current supply timing is controlled so as to apply a machining voltage to the machining gap by emitting a machining pulse. On location.

[Action]

The control device for a wire electric discharge machine according to the present invention is configured as described above, and operates as follows. That is,
The control device of the wire electric discharge machine generates a detection pulse, i.e., a spike voltage, having a width sufficiently shorter than a machining pulse width for checking a residual ion concentration in a machining fluid existing in a gap between a wire electrode and a workpiece. By applying, the insulation recovery state of the machining fluid present in the machining gap is detected, and the machining discharge voltage is immediately applied in accordance with the detection signal, so that the discharge current always becomes a normal discharge and is used only as the discharge energy. . Moreover, even if an abnormal discharge state occurs, the normal state can be reliably detected in a short time, and the discharge current can be immediately supplied between the poles to perform the discharge machining of the workpiece.
In addition, since the discharge current is supplied only when the abnormal discharge does not occur, the abnormal discharge does not occur between the poles.

That is, in the control device of this wire electric discharge machine, the spike voltage is applied to the machining gap by emitting a detection pulse having a width sufficiently shorter than the machining pulse width, and in particular, the spike voltage is set beforehand during the pulse pause time. It is applied continuously at regular intervals until the insulation of the working fluid is restored in the working gap. Then, in response to the spike voltage by the detection pulse being a voltage equal to or higher than a predetermined set value indicating the insulation recovery of the machining fluid, generating a machining pulse at a timing at which the next detection pulse is issued, A processing voltage is applied to the processing gap. In particular, the processing pulse rise time and the processing pulse pause time width of the processing pulse are determined based on the fixed time interval of the detection pulse, and change according to the timing of the insulation recovery of the processing liquid. .

Therefore, even if an abnormal discharge state occurs, the control device of the wire electric discharge machine can reliably detect the normal state in a short time and immediately supply a discharge current between the poles to perform the discharge machining of the workpiece. Therefore, the electric discharge machining speed for the workpiece can be greatly improved.

〔Example〕

Hereinafter, an embodiment of a control device for a wire electric discharge machine according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block circuit diagram showing an example of a power supply device for wire electric discharge machining applied to a control device of a wire electric discharge machine according to the present invention.

In the wire electric discharge machine, a workpiece, that is, a workpiece 2 is installed on a workpiece mounting table. Generally, the work mount is configured to be movable in the horizontal direction, that is, in the X and Y directions. That is, the work mounting table on which the work 2 is mounted is moved in accordance with the processing condition of the work 2 by a command from the NC device.
And the servo function is repeatedly advanced by a servo feed mechanism 7 driven by a servo motor 8 between the wire electrode 1 supplied to the wire head and the wire electrode 1 supplied to the wire head.
The workpiece 2 is subjected to electrical discharge machining into a predetermined machining shape by the relative movement between the two.

Further, wire heads are provided above and below the workpiece 2, and these wire heads are composed of a power supply, a power supply holding member, a die guide member, a working liquid jet nozzle, and the like.
A wire electrode 1 fed from an automatic wire feeder via a roller guide or the like passes through a die guide member provided in an inner cylinder body of the upper wire head, discharges the workpiece 2 and then discharges the inner cylinder of the lower wire head. It is sent through the body to a take-up reel, a used wire reservoir, or the like.

By the way, in the wire electric discharge machine, if the gap between the poles is a distance at which the dielectric breakdown can occur, the discharge is started immediately, the two poles are connected by an arc column, a discharge current _Ip flows, and electric discharge machining is performed on the workpiece 2. Done. Then, when the machining clock reaches the pause time R, the discharge state stops. Here, the wire electrode 1
And for applying the inter-electrode voltage V _G relative to the workpiece 2, the machining power supply 3, and opening and closing the working DC power supply with a discharge pulse switch such as a transistor for processing a pulse in the discharge current control circuit, the wire electrode A discharge pulse voltage is applied between both poles of the workpiece 1 and the workpiece 2 to supply discharge energy. The work 2 is melted by the discharge energy and the work 2 is melted.
Can be subjected to electrical discharge machining.

Moreover, electrode-to-electrode state of a wire electric discharge machine, the machining fluid state, namely residual ions of whether present in the machining fluid state, processing waste, abnormality does not rise the electrode-to-electrode voltage V _G on the cause of wire vibration Discharge may occur. If this abnormal discharge period continues for a predetermined time or more, the wire that is the wire electrode 1 is broken, and it becomes impossible to perform electric discharge machining.

By the way, when a discharge current is supplied to the gap 17 last time, ions are generated in the machining fluid existing in the machining gap between the wire electrode 1 and the workpiece 2, that is, the gap 17.
Residual ions remain in the 17 working fluid. When a discharge current is supplied to the gap 17 in a state where the ions remain in the machining fluid without disappearing, discharge immediately occurs in that portion without rising to the discharge voltage, resulting in abnormal discharge, which actually occurs. There is a disadvantage that a discharge voltage is not applied to a portion to be caused to occur.

Therefore, when a discharge current is supplied in a state where ions in the machining fluid in the gap 17 have completely disappeared, a normal discharge voltage is applied. Therefore, the residual ion concentration can be checked by applying the spike voltage V _S by the detection pulse sufficiently shorter than the pulse width to the gap 17. That is, if the spike voltage V _S is above the level of the predetermined discharge voltage V _L, as already disappeared ion concentration in the machining fluid, it can be applied to a normal discharge voltage, and supplies the discharge current between the electrodes 17.

The control device of the wire electric discharge machine controls the spike voltage V _S by the detection pulse for checking the residual ion concentration in the machining fluid existing in the machining gap between the wire electrode 1 and the workpiece 2, that is, in the gap 17, and suspends the pulse. The discharge current supply timing is controlled so that a pulsed discharge current is supplied in accordance with the recovery of the insulation of the machining fluid by detecting the state of insulation of the machining fluid by applying to the machining gap within a time. is there. Moreover, the control device of this wire electric discharge machine
V _S is to the insulating machining fluid is restored, it detects the state of the ion concentration by one or a plurality applied.

The control device of this wire electric discharge machine has a spike voltage V _S
During the pulse pause time, as shown in FIG. 2, is continuously applied at predetermined time intervals t ₀ until the insulation of the machining fluid is restored to the gap 17, and the spike voltage V due to the detection pulse is applied. _S is a predetermined set value indicating the insulation recovery of the working fluid
At the timing when the next detection pulse is issued in response to the voltage being equal to or higher than _VL , a certain time interval between the detection pulses
machining gap issues a machining pulses the t ₀ in the reference machining pulse rise time and the machining pulse pause duration are determined
The discharge current supply timing is controlled so that a processing voltage is applied to the substrate 17.

As shown in FIG. 1, a periodic signal for electric discharge machining is transmitted from a transmitter, that is, a reference clock generation circuit 12, in the power supply device for wire electric discharge machining. Further, the pulse width P and downtime R of the discharge current I _P is controlled by the machining pulse generator 14. The electric signal of the machining pulse generated by the machining pulse generating circuit 14 is turned on or off by the prohibition gate 15, and a discharge voltage, that is, a gap voltage V is applied to the gap 17 between the wire electrode 1 and the workpiece 2. It is input to the processing power supply 3 depending on whether or not to apply _G.

Therefore, the electric signal of the processing pulse having the pulse width P and the pause time R controlled by the processing pulse generation circuit 14 based on the periodic signal transmitted from the reference clock generation circuit 12 is transmitted to the processing power supply 3 through the inhibition gate 15. Sent in. By the pulse signal from the processing pulse generating circuit 14 is input to the machining power supply 3, a predetermined discharge current I _P in the machining power supply 3 in response to the pulse signal is passed through the machining gap 17, between contacts 17 inter-electrode voltage V _G is applied to.

A diode switch circuit 5 is incorporated between the wire electrode 1 and the processing power supply 3 so as to prevent a reverse current from flowing. The electric signal from the reference clock generation circuit 12 is input to the ion concentration check pulse generation circuit 13. In the ion density check pulse generating circuit 13 applies a discharge voltage i.e. inter-electrode voltage V _G through a predetermined time period t ₀ emits an electrical signal in ion concentration check pulse or spike voltage V _S.

The electric signal of the spike voltage V _S is input to the ion concentration detection power supply 4 and also to the waveform correction circuit 10. In response to an electrical signal input to the ion concentration detecting power source 4, an ion concentration from the detected power supply 4 predetermined spike voltage V _S is applied to the machining gap between the wire electrode 1 and the workpiece 2. A diode switch circuit 6 is incorporated between the wire electrode 1 and the ion concentration detection power supply 4 so as to prevent current from flowing backward.

Furthermore, in the buffer amplifier 9 provided in the machining power supply device for wire electric discharge machining, the pulse of the ion concentration check applied to the gap to check the ion concentration during machining between the gaps, that is, the spike voltage V _S is applied. adjust the voltage value V _S which is suitable signals to the control, the waveform correction circuit 10 an electrical signal
To enter. Voltage V _S of the spike voltage emitted from the waveform correction circuit 10 is compared in the comparator 11 and the voltage value V _L of the predetermined ion concentration level predetermined voltage. comparator
By comparison by 11, if the voltage value V _S of the spike voltage is above the voltage value V _L of ion concentration level setting voltage, and in a conducting state by opening the circuit of the prohibited gate 15, for machining from the machining pulse generator 14 Control is performed so that a pulse electric signal is input to the processing power supply 3. Further, if the voltage value V _S of the spike voltage is less than the voltage value V _L of ion concentration level setting voltage, and a non-conductive state to close the circuit of the prohibited gate 15, the machining pulses from the machining pulse generator 14 Control is performed so that an electric signal is not input to the processing power supply 3. The discrimination reference voltage of the comparator 11 is set by the potentiometer 16.

The principle of the control device for a wire electric discharge machine according to the present invention will be described with reference to FIG. In FIG.
When the elapsed time t (μs) is plotted on the horizontal axis, the waveform (A) shows the no-load voltage V ₀ , and the waveform (B) shows the gap voltage V _G
Are shown, also the waveform (C) shows a discharge current I _W. Discharge current
For I _W, as shown at a, is only the discharge current during normal discharge, the discharge current of the abnormal discharge during which does not contribute to electric discharge machining can be seen that absent. That is, in the waveform indicating the inter-electrode voltage V _G, a spike voltage V _S is a detection pulse for ion density check is applied to the machining gap 17 at a predetermined clock, the spike voltage V _S is predetermined discharge voltage, in other words applies the inter-electrode voltage V _G for the first time discharge machining becomes ion concentration level setting voltage V _L over voltage. Curve D is an inter-electrode insulation recovery curve showing the voltage value of the spike voltage V _S applied to the inter-electrode 17 between the wire electrode 1 and the workpiece 2. Therefore, after detecting the ion concentration state of the working fluid in the gap 17,
Since a discharge voltage is applied to the gap 17 for the first time, no abnormal discharge state occurs in the gap 17.

An example of the operation of the control device of the wire electric discharge machine according to the present invention will be described with reference to FIGS. 1, 2, 3A and 3B. FIGS. 3A and 3B are flow charts showing one embodiment of the operation of the control device of the wire electric discharge machine according to the present invention.

First, the operation switch of the wire electric discharge machine is turned on, and the servo motor 8, the wire supply device, the machining fluid supply device and the like are turned on (step 50). In order to perform electrical discharge machining on the workpiece 2, a reference clock is generated by the reference clock generation circuit 12 (step 51). Upon receiving the electric signal of the reference clock, the electric signal of the machining pulse is generated based on the pulse width P and the pause time R set for performing the electric discharge machining by the machining pulse generating circuit 14 (step 52).

Since no discharge voltage is applied to the gap 17 at the beginning of the electric discharge machining, no ions are generated in the machining fluid in the gap 17. Therefore, the prohibition gate 15 is open, and the electric signal of the processing pulse from the processing pulse generation circuit 14 conducts the prohibition gate 15 (step 53). The electric signal of the machining pulse passing through the prohibition gate 15 is input to the machining power supply 3,
Discharge current I _P with a voltage and a pulse width required for electric discharge machining in accordance with the electric signal is passed through the machining gap 17, the machining gap voltage or discharge voltage V _G is applied to the machining gap 17 (step 54).

Workpiece 2 is discharge machining by discharge voltage V _G to the machining gap 17 of the wire electrode 1 and the workpiece 2 is applied (step 55). It is determined whether finishing or machining of the machining surface of the workpiece 2 is completed (step 56), and if it is completed, the operation of the wire electric discharge machine is stopped (step 5).
7).

When the finishing or processing of the processing surface of the workpiece 2 has not been completed, the machining gap by flowing a discharge current I _P between the poles 17
Since there is a possibility that ions are generated in the machining fluid 17, the ion concentration in the machining fluid in the gap 17 is determined by the pulse pause time R
Detect within. In this case, the processing pulse generation circuit 14
Electric signal processing pulse prohibition gate 15 as the discharge voltage V _G is not applied to the other words the machining gap 17 from being input to the machining power supply 3 is closed from (step 58). After the discharge voltage V _G has passed the time t ₀ is within the pulse pause time R is applied to the machining gap 17 (step 59), the reference clock by the substrate clock generating circuit 12 for generating a pulse for ion concentration detected Is generated (step 60). Generating an electrical signal to generate a detected pulse or spike voltage V _S with a predetermined voltage and pulse width by ion density check pulse generating circuit 13 by an electrical signal of the reference clock (step 61).

The electric signal generated by the ion concentration check pulse generation circuit 13 is input to the waveform correction circuit 10 and the electric signal is input to the detection power supply 4. spike voltage V _S corresponding to the electrical signal is charged (step 62). Spike voltage V _S generated by the detection power source 4 is applied to the machining gap 17 (step 63). In this case, the voltage value of the spike voltage V _S by the ion concentration of the working fluid between the poles 17 varies.
That is, the voltage value of the spike voltage V _S when the ion concentration is high becomes low, the spike voltage when ion concentration is low
The voltage value of V _S increases. The voltage value of the spike voltage V _S is input to the buffer amplifier 9 is an electrical signal, the electrical signal is adjusted to a voltage value suitable for the control (step 64).

Next, the electric signal having the voltage value is applied to the waveform correcting circuit 10.
The waveform is corrected in (step 65). Voltage signal waveform corrected is input to the comparator 11, the electrical signal or spike voltage V _S is, determines whether or not higher than the predetermined voltage value V _L (step 66).

When the spike voltage V _S is higher than the predetermined voltage value V _L is
Ion concentration of the working fluid between the poles 17 are lowered, as is already state become no state or discharge machining conditions to be abnormal discharge by applying a discharge voltage V _G between the poles 17 are in place, the machining gap for applying a discharge voltage V _G to 17, the process proceeds to step 51 (a).

Further, when the spike voltage V _S is lower than the predetermined voltage value V _L, the ion concentration of the working fluid between the poles 17 is high, the electric discharge machining conditions not fully equipped, the discharge voltage V _G to the machining gap 17 since in a state where the applied becomes abnormal discharge, without applying a discharge voltage V _G to the machining gap 17. In this case, counting the number of times of application N spike voltage V _S (67). While the number N of times of application of the spike voltage V _S is smaller than the predetermined number N _{0 of} times of application, the application of the spike voltage V _S is continuously performed to the gap 17 (step 68). Therefore, after the time t _0, the process to generate the reference clock by the reference clock generating circuit 12 for generating a pulse for ion concentration detection proceeds to step 59 (D).

Further, the number of applications applied number N of predetermined voltage spike V _S
When even if greater than N ₀ not lower the ion concentration of the working fluid between the poles 17, the deposition of the processing refuse into the machining gap 17, wire vibration, the inter-electrode voltage when there is another cause of leakage, such as rise If not, an abnormal signal is issued (step 69), and the wire electric discharge machine is stopped (E).

〔The invention's effect〕

The control device for a wire electric discharge machine according to the present invention is configured as described above, and operates as follows. In other words, the control device of this wire electric discharge machine uses a spike caused by a detection pulse having a width sufficiently shorter than the width of the machining pulse for checking the residual ion concentration in the machining fluid existing in the gap between the wire electrode and the workpiece. By applying a voltage, the insulation recovery state of the machining fluid present in the machining gap is detected, and a discharge voltage is immediately applied in response to the detection signal. The pulse power is used as electric discharge energy for electric discharge machining of a workpiece, and unnecessary abnormal electric discharge energy that does not contribute to electric discharge machining of the workpiece can be completely eliminated.

Further, since the spike voltage is extremely small as power consumption energy, there is no problem in terms of energy consumption. In addition, even if an abnormal discharge state occurs, the normal state can be reliably detected in a short time, and the discharge current can be immediately supplied to the gap to perform the discharge machining of the workpiece.
A wasteful off-period can be eliminated, and the time required to return to normal discharge is extremely short, so that the electric discharge machining speed for the workpiece can be greatly improved. In addition, since the discharge current is supplied only when no abnormal discharge occurs, no abnormal discharge is generated between the poles, the work surface is not adversely affected, and the work surface accuracy can be improved. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a power supply device for wire electric discharge machining applied to a control device of the wire electric discharge machine according to the present invention, and FIG. 2 shows a control state of a control device of the wire electric discharge machine according to the present invention. Voltage waveform diagram shown as a waveform,
3 (A) and 3 (B) are flowcharts showing an example of the operation of the control device of the wire electric discharge machine according to the present invention, and FIG. 4 shows the control state of the control device of the conventional wire electric discharge machine. It is a voltage waveform diagram shown as a waveform. 1 ... wire electrode, 2 ... workpiece, 3 ... power supply for processing,
4 ... Detection power supply, 5,6 ... Diode switch circuit, 1
0: Waveform correction circuit, 11: Comparator, 12: Reference clock generation circuit, 13: Pulse generation circuit for ion concentration check, 14: Pulse generation circuit for processing, 15: Prohibition gate, 16: Po Tensiometer, 17 ... Between poles.

Claims (1)

(57) [Claims] 1. A spike voltage generated by a detection pulse having a width sufficiently shorter than a processing pulse width for checking a residual ion concentration in a processing liquid existing in a processing gap between a wire electrode and a workpiece. A predetermined setting which is applied until the insulation of the machining fluid is restored to the machining gap continuously at regular intervals set in advance during the time, and the spike voltage by the detection pulse indicates the restoration of the insulation of the machining fluid. In response to the voltage being equal to or higher than the value, at the timing of issuing the next detection pulse, the processing pulse rising time and the processing pulse pause time width are determined based on the fixed time interval of the detection pulse. A control device for a wire electric discharge machine, wherein a discharge current supply timing is controlled so as to emit a pulse and apply a machining voltage to the machining gap.