JPH06339815A - Electric discharge machining power unit - Google Patents

Abstract

PURPOSE:To provide an electric discharge machining power unit which conducts highly precise electric discharge machining by setting average voltage between a discharge electrode and a machining electrode at zero for prevention of electrolytic corrosion. CONSTITUTION:By adjusting voltage level VS or level VS and its time length tauONS at an opposite polarity to a polarity to be applied at the time of discharge stoppage (time, tauOFF) and electric discharge, average polarity-to-polarity voltage is adjusted so as to obtain zero to solve problems such as electrolytic corrosion generated at a work when d.c. voltage for electric discharge is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining power supply device, and more particularly to an electric discharge machining power supply device for suppressing the occurrence of electrolytic corrosion (electrolytic corrosion) of a work.

[0002]

2. Description of the Related Art For example, in a wire electric discharge machining power supply device, a wire electrode immersed in a machining liquid such as water is used as a negative electrode, a workpiece is a positive electrode, and a pulsed discharge voltage is applied between both electrodes. Is applied. When water is used as the working fluid, not only the problem that electrolysis current flows to cause electrolysis (action), that is, electrolytic corrosion, and the accuracy of the finished surface of the work surface deteriorates, but also the work is damaged. There is also the problem of being lost. Therefore, conventionally, a technique has been adopted in which an average voltage is made zero by applying a voltage reverse to the applied voltage at the time of electric discharge machining between the electrode and the work during non-machining. An example of this technique is disclosed in JP-A-60-201826. In this publication, the time for applying a voltage having a polarity opposite to that at the time of machining between the wire electrode and the work is adjusted so that the average machining voltage becomes zero to prevent electrolytic corrosion.

[0003]

As described above, in the conventional electric discharge machining power supply device, in order to prevent electrolytic corrosion, a voltage having a polarity opposite to that of electric discharge machining is applied between the electrode and the work during non-electric discharge machining. The time length of the applied voltage is adjusted so that the average voltage becomes zero.

However, in the usual electric discharge machining, a DC voltage is applied between the wire electrode and the work electrode to generate an electric discharge, and when the electric discharge occurs, the electric discharge machining is performed for a predetermined time, and then the DC voltage is applied. Is stopped to stop the electric discharge machining, and subsequently, a process of applying a DC voltage for causing electric discharge is repeatedly performed. In the above-mentioned conventional technique, a DC voltage having a polarity opposite to that of the DC voltage at the time of electric discharge machining is supplied during this discharge pause period. However, since the application time length of the DC voltage adjusted to make the average voltage zero is limited by the discharge rest period, there is a limit in the adjustment range, and there are cases where the average voltage cannot be made zero. In some cases, there is a problem that electrolytic corrosion will occur.

Therefore, the object of the present invention is to always make the average voltage between the wire electrode and the work electrode zero in any case to prevent electrolytic corrosion and enable high-precision electric discharge machining. To provide a device.

[0006]

In order to solve the above-mentioned problems, the electric discharge machining power supply device according to the present invention performs electric discharge machining by applying a voltage with a predetermined polarity between the machining electrode and the work electrode. In the electric discharge machining power supply device to be performed, first means for detecting an average voltage between the electrodes, and a reverse polarity voltage having a reverse polarity to the voltage having the predetermined polarity during a pause period of discharge by the voltage having the predetermined polarity. Second applied between the electrodes
And the level of the reverse polarity voltage output from the second means in accordance with the difference between the average voltage detected by the first means and a predetermined allowable value, the average voltage becomes zero. And a third means for controlling the direction.

[0007]

In the present invention, the inter-electrode average voltage can be made zero by adjusting the voltage level applied at the time of the discharge stop and having the opposite polarity to the polarity applied at the time of discharge, or the level and the time length thereof.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows output waveforms of a voltage between electrodes applied between electrodes of a wire electrode and a work electrode from an electric discharge machining power supply device according to the present invention, and ON-OFF timings of a main power supply and a sub power supply. In FIG. 1, a state where a negative voltage is applied to the wire electrode has a predetermined polarity, and a state where a positive voltage is applied to the wire electrode has a reverse polarity. Wire electric discharge machine or die-sinking electric discharge machine, material of machining electrode or workpiece,
Depending on the processing conditions and the like, whether to process the processing electrode with a positive voltage or the work with a positive voltage is a matter to be determined in advance. In short, the voltage of the predetermined polarity is the polarity of the one that is actually processed by electric discharge. This predetermined polarity is hereinafter referred to as positive polarity. A positive voltage is applied between the electrodes at the electric discharge machining start time T0, and when electric discharge occurs at time T1, electric discharge machining is performed. At this time, the voltage between the electrodes sharply decreases. Time point T2 when the first electrical discharge machining ends
Thus, the applied voltage becomes zero and the voltage between contacts also becomes zero. This single electric discharge machining processing time (T0-T2) is represented by τ _ONM and is 2
It is about 20 μsec. The same as this EDM processing time
After the pause time τ _{OFF of} ˜20 μsec has elapsed, the second electric discharge machining process is started at time T5, and the positive voltage is applied between the electrodes. The electric discharge machining is performed at the time T6 when the electric discharge occurs, and the second idle period starts from the time T7.

In this embodiment, the positive voltage is supplied from the main power source and the reverse polarity voltage is supplied from the sub power source. That is, as shown in FIG. 1, the first supply of the positive voltage from the main power source is performed only during τ _ONM , and during the period of τ _OFF , the supply is stopped and then the second supply is performed. Further, the reverse polarity voltage from the sub power supply is supplied for the time of τ _ONS within the τ _OFF period. τ _ONS starts at T3 and ends at T4.
In this embodiment, the reverse polarity voltage supply time τ _ONS and its level are adjusted so that the average voltage becomes zero.

FIG. 2 is a block diagram showing the configuration of an embodiment of the electric discharge machining power supply device according to the present invention. NC
From the device 1, a VM command signal for commanding the voltage level VM applied between the wire electrode 7 and the work electrode 8 during electric discharge machining is sent to the main power supply voltage adjusting unit 2. Main power supply voltage adjustment unit 2
Receives the VM command signal and outputs the stabilized voltage VM.
From the main power output unit 3, the power supply terminals 7A and 7A of the wire electrode 7 are connected.
A positive voltage is supplied to B. When the positive voltage is applied between the wire electrode 7 and the work 8, a discharge is generated and the work 8 is subjected to electric discharge machining. At this time, the current IM flows from the wire electrode 7 to the main power supply output section 3.

In response to the VS command signal from the control unit 6, the sub power supply voltage adjusting unit 4 outputs a constant polarity reverse polarity voltage to the sub power supply output unit 5. From the sub power supply output unit 5, the level V
The reverse polarity voltage of S and time τ _{ONS is} the power supply 7 of the wire electrode 7.
A, 7B is supplied. At this time, the current IS flows from the sub power supply output section 5 toward the wire electrode 7. Here, since the sub power supply output unit 5 is not for the purpose of performing processing, Is has a sufficiently small value as compared with IM. The control unit 6 is NC
Receiving a τ _OFF signal indicating the discharge rest period supplied from the device 1 and a voltage signal applied to the wire electrode 7,
The sub power supply voltage adjusting unit 4 is instructed to output the reverse polarity voltage VS. Further, the control unit 6 sends τ _ONM that specifies the generation time of the positive polarity voltage and τ _ONS that specifies the generation time of the reverse polarity voltage to the main power supply output unit 3 and the sub power supply output unit 5, respectively. The positive polarity voltage and the reverse polarity voltage are generated in the sequence shown in FIG. At this time, the control unit 6 detects an average voltage of the voltages from the power supply terminals 7A and 7B of the wire electrode 7,
The level VS of the reverse polarity voltage or the level VS and its time length τ _ONS are adjusted.

FIG. 3 is a flow chart showing an operation processing procedure of the control unit 6 for adjusting the reverse polarity voltage in order to make the inter-electrode average voltage zero in this embodiment. For example,
The adjustment process of this embodiment is started every 100 msec.
The inter-electrode average voltage VG is detected based on the voltage from the power supply terminals 7A and 7B of the wire electrode 7 (step S1), and the absolute value of the detected average voltage VG is a predetermined allowable voltage Pr (ideally zero). Is determined (step S2), and if it is smaller, it is determined that the current adjustment does not cause problems such as electrolytic corrosion, and detection of the average voltage VG between poles in the interval following step S1. To do. On the other hand, in step S2, when the absolute value of the average voltage becomes larger than Pr, there is a problem such as electrolytic corrosion. Therefore, the level and time length of the reverse polarity voltage VS are adjusted and the average voltage becomes zero. Control to become. Therefore, step S3
In step S4, it is determined whether the average voltage VG is positive or negative. If the average voltage VG is positive, the voltage VP to be subtracted from the current reverse polarity voltage VS is determined (step S4), and the reverse polarity voltage to be applied next is VS-VP.
(Step S5), and the process returns to step S1 again. When the average voltage VG is negative in step S3, the predetermined value VP to be added to the current reverse polarity voltage VS is determined (step S6), and the reverse polarity voltage to be applied next is set as VS + VP (step S7). Step S
Return to processing of 1.

In the above-described embodiment, the reverse polarity voltage for adjusting the average voltage to zero is targeted at the level VS, but if the time length τ _ONS is adjusted in addition to the level VS, the adjustment range is further increased. It is enlarged and highly accurate adjustment is possible.

The flowchart of FIG. 4 shows the operation processing procedure of another embodiment of the present invention. The present embodiment shows a process in a state (open state) in which discharge is not performed even if a voltage for discharge is applied between the electrodes. In other words, this is the open state when the distance between the wire electrode and the work becomes longer and the discharge is stopped for some reason during the approach stage of shifting to the actual electric discharge machining or during the electric discharge machining where the positive polarity voltage is applied. If it continues for a long time, the above-mentioned problem of electrolytic corrosion occurs. The present embodiment solves this problem.

Referring to FIG. 4, first, when the τ _ONM “ON” signal for instructing the application of the positive voltage is output (step S11), the open counter Tc for detecting the open state time is started. After (Step S1
2) Determine whether or not discharge has occurred (step S1)
3). The occurrence of discharge can be easily determined, for example, by detecting that the voltage between contacts has dropped below a certain value. If discharge has not occurred, it is determined whether or not the open counter has counted Tc (for example, 50 μsec) (step S14). When it is determined in step S13 that discharge has occurred, and when the open counter _measures Tc in step S14, the signal τ _ONM is _set to “OFF”.
Then, the timer is started (step S15). Here, when the timer measures time Td (which is shown in FIG. 1 and corresponds to the margin for the delay of the output element and the delay of the current due to the inductance of the cable, for example, 1 μsec is set) (step S16), Reverse polarity voltage V
The signal τONS for outputting S is turned “ON” (step S17), and the open counter is started again (step S18). Next, it is determined whether discharge has occurred (step S19), and if discharge has not occurred, it is determined whether the open counter has elapsed time Tc (step S2).
0), if not elapsed, the process returns to step S19. When it is determined in step S19 that discharge has occurred, or when the time Tc is measured in step S20, the signal τ _{ONS is set} to “OFF” (step S21),
After measuring the time Td by the timer (step S2
2), the process returns to step S1.

According to the embodiment shown in FIG. 4, even in the open state, for example, an alternating voltage of several KHz is output at the timing of τ _ONM and τ _ONS , and the effect becomes remarkable.

[0017]

As described above, in the electric discharge machining power supply device according to the present invention, by adjusting the voltage level of the polarity opposite to the polarity applied at the time of the discharge applied at the time of the discharge pause or the level and the time length thereof. Since the average voltage between contacts is adjusted to zero, problems such as electrolytic corrosion that occur when a DC voltage for discharge is applied are solved, and the adjustment range is expanded to enable more accurate electrical discharge machining. Becomes

[Brief description of drawings]

FIG. 1 is a diagram for explaining the operation of an embodiment of an electric discharge machining power supply device according to the present invention.

FIG. 2 is a configuration block diagram showing an embodiment of an electric discharge machining power supply device according to the present invention.

FIG. 3 is a flowchart showing an operation processing procedure of an embodiment of the electric discharge machining power supply device according to the present invention.

FIG. 4 is a flowchart showing an operation processing procedure of another embodiment of the electric discharge machining power supply device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 NC device 2 Main power supply voltage adjustment unit 3 Main power supply output unit 4 Sub power supply voltage adjustment unit 5 Sub power supply output unit 6 Control unit 7 Wire electrodes 7A, 7B
Power supply 8 work

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[Procedure amendment]

[Submission date] October 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

[0006]

In order to solve the above-mentioned problems, the electric discharge machining power supply device according to the present invention performs electric discharge machining by applying a voltage with a predetermined polarity between the machining electrode and the work electrode. In the electric discharge machining power supply device to be performed, the first means for detecting the average voltage between the both electrodes, and the voltage of the polarity opposite to the voltage of the predetermined polarity during the suspension period of the discharge by the voltage of the predetermined polarity The second means applied between both electrodes, and the voltage of the opposite polarity output from the second means according to the difference between the average voltage detected by the first means and a predetermined allowable value. And a third means for controlling the level so that the average voltage becomes zero.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

FIG. 3 is a flow chart showing an operation processing procedure of the control unit 6 for adjusting the reverse polarity voltage in order to make the inter-electrode average voltage zero in this embodiment. For example,
The adjustment process of this embodiment is started every 100 msec.
The inter-electrode average voltage VG is detected based on the voltage from the power supply terminals 7A and 7B of the wire electrode 7 (step S1), and the absolute value of the detected average voltage VG is a predetermined allowable voltage Pr (ideally zero). Is determined (step S2), and if it is smaller, it is determined that the current adjustment does not cause problems such as electrolytic corrosion, and detection of the average voltage VG between poles in the interval following step S1. To do. On the other hand, in step S2, when the absolute value of the average voltage becomes larger than Pr, there is a problem such as electrolytic corrosion. Therefore, the level and time length of the reverse polarity voltage VS are adjusted and the average voltage becomes zero. Control to become. Therefore, step S3
, It is determined whether the average voltage VG is positive or negative. If the average voltage VG is positive, the voltage VP to be subtracted from the current reverse polarity voltage VS is determined (step S6), and the reverse polarity voltage to be applied next is VS-VP.
(Step S7), and the process returns to step S1 again. When the average voltage VG is negative in step S3, a predetermined value VP to be added to the current reverse polarity voltage VS is determined (step S4), and the reverse polarity voltage to be applied next is set as VS + VP (step S5). Step S
Return to processing of 1.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be amended] Detailed explanation of the invention

[Correction method] Change

[Correction content]

Referring to FIG. 4, first, when the τ _ONM “ON” signal for instructing the application of the positive voltage is output (step S11), the open counter Tc for detecting the open state time is started. After (Step S1
2) Determine whether or not discharge has occurred (step S1)
3). The occurrence of discharge can be easily determined, for example, by detecting that the voltage between contacts has dropped below a certain value. If discharge has not occurred, it is determined whether or not the open counter has counted Tc (for example, 50 μsec) (step S14). When it is determined in step S13 that discharge has occurred, τ _ON control is performed to set a predetermined discharge time (step S23), and the signal τ _ONM is _set to “OFF” (step S15). Also, when the open counter _measures Tc in step S14, the signal τ _ONM is _set to “O”.
FF "(step S15), and the timer is started. Here, the timer causes the time Td (shown in FIG.
Corresponding to the delay of the output element and the margin for the current delay due to the inductance of the cable, for example, 1 μsec is set) (step S16), the signal τONS for outputting the reverse polarity voltage VS is turned “ON”. Then (step S17), the open counter is started again (step S18). Next, it is determined whether discharge has occurred (step S19). If discharge has not occurred, it is determined whether the open counter has elapsed time Tc (step S20). If not, the process returns to step S19. . When it is determined in step S19 that discharge has occurred, or when the time Tc is measured in step S20, the signal τ _{ONS is set} to “OFF” (step S2
1) After measuring the time Td by the timer (step S
22) and returns to the process of step S11.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

[Procedure correction 6]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 4

[Correction method] Change

[Correction content]

[Figure 4] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 20, 1994

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In order to solve the above-mentioned problems, the electric discharge machining power supply device according to the present invention performs electric discharge machining by applying a voltage with a predetermined polarity between the machining electrode and the work electrode. In the electric discharge machining power supply device to be performed, the first means for detecting the average voltage between the both electrodes, and the voltage of the polarity opposite to the voltage of the predetermined polarity during the suspension period of the discharge by the voltage of the predetermined polarity The second means applied between both electrodes, and the voltage of the opposite polarity output from the second means according to the difference between the average voltage detected by the first means and a predetermined allowable value. And a third means for controlling the level so that the average voltage becomes zero.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

FIG. 3 is a flow chart showing an operation processing procedure of the control unit 6 for adjusting the reverse polarity voltage in order to make the inter-electrode average voltage zero in this embodiment. For example,
The adjustment process of the present embodiment is started every 100 msec, and first, the inter-electrode average voltage VG is detected based on the voltage from the power supply terminals 7A and 7B of the wire electrode 7 (step S1), and the detected average voltage VG is absolute. Allowable voltage Pr whose value is predetermined
It is determined whether or not it is smaller than (ideally zero) (step S2), and if it is smaller, it is considered that electrolytic corrosion does not pose a problem in the current adjustment, and the pole in the interval next to step S1 is determined. The inter-average voltage VG is detected. on the other hand,
In step S2, when the absolute value of the average voltage becomes larger than Pr, there is a problem such as electrolytic corrosion. Therefore, the level and time length of the reverse polarity voltage VS are adjusted and the average voltage becomes zero. Control in the direction. Therefore, in step S3, it is determined whether the average voltage VG is positive or negative. If the average voltage VG is positive, the voltage V to be subtracted from the current reverse polarity voltage VS.
P is determined (step S6), the reverse polarity voltage to be applied next is set as VS-VP (step S7), and the process returns to step S1. In step S3, the average voltage V
When G is negative, a predetermined value VP to be added to the current reverse polarity voltage VS is determined (step S4), and the reverse polarity voltage to be applied next is set as VS + VP (step S4).
5) and returns to the process of step S1.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Referring to FIG. 4, first, when the τONM "ON" signal for instructing the application of the positive polarity voltage is output (step S11), the open counter Tc for detecting the open state time is started. (Step S1
2) Determine whether or not discharge has occurred (step S1)
3). The occurrence of discharge can be easily determined, for example, by detecting that the voltage between contacts has dropped below a certain value. If discharge has not occurred, it is determined whether or not the open counter has measured Tc (for example, 50 μsec) (step S14). When it is determined in step S13 that discharge has occurred, τON control is performed to set a predetermined discharge time (step S23), and the signal τONM is set to “OF”.
F "(step S15). Also, step S14
Even when the open counter measures Tc at
The ONM is turned "OFF" (step S15), and the timer is started. Here, when the timer measures time Td (corresponding to the margin for the delay of the output element and the delay of the current due to the inductance of the cable, which is shown in FIG. 1, for example, 1 μsec is set) (step S
16), a signal τON for outputting the reverse polarity voltage VS
S is turned "ON" (step S17), and the open counter is started again (step S18). Next, it is determined whether or not discharge has occurred (step S19). If discharge has not occurred, it is determined whether or not the open counter has elapsed time Tc (step S20). If not, the process returns to step S19. . When it is determined in step S19 that discharge has occurred, or when the time Tc is measured in step S20, the signal τONS is turned "OFF" (step S21), and after the time Td is measured by the timer (step S22). , And returns to the process of step S11.

Claims (3)

[Claims] 1. An electric discharge machining power supply device for performing electric discharge machining by applying a voltage with a predetermined polarity between both electrodes of a machining electrode and a work electrode, wherein a first voltage for detecting an average voltage between both electrodes is detected. A second means for applying a reverse polarity voltage having a reverse polarity to the voltage of the predetermined polarity between the electrodes during a rest period of discharge by the voltage of the predetermined polarity; and detection by the first means. Third means for controlling the level of the reverse polarity voltage output from the second means in the direction in which the average voltage becomes zero according to the difference between the average voltage and a predetermined allowable value. An electric discharge machine power supply device characterized by comprising. 2. The electric discharge machining power supply device according to claim 1, wherein the third means controls the level and time length of the reverse polarity voltage so that the average voltage becomes zero. 3. A fourth means for detecting that an open state in which no discharge has occurred despite the application of the voltage of the predetermined polarity has continued for a predetermined time or more; The electric discharge machining power supply device according to claim 1 or 2, further comprising: fifth means for alternately and repeatedly generating the voltage of the predetermined polarity and the voltage of the opposite polarity when detected.