JPH1170414A - Work rustproofing method and device for wire discharge machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent rusting on a work surface left in work liquid during unoperating working. SOLUTION: This rustproofing device is constituted so as to work a work piece 1 by discharge, generated by applying voltage between the work piece 1 in work liquid and a wire electrode 2. In this case, the following are equipped: a means for judging unoperating working and the existence of the work piece in the work liquid, anticorrosion electrodes 12a and 12b installed in the work liquid, and an anticorrosion power source 14 for applying voltage between the work piece 1 and the anticorrosion electrodes 12a and 12b during unoperating working, so as to eliminate the electric corrosion in the work piece 1, due to the release of the metallic ion of the work piece 1 into the work liquid from the work piece 1. The anticorrosion power source 14 is an A.C. power source or a high-frequency A.C. power source for applying voltage so that mean voltage, between a D.C. power source, the work piece 1 and the anticorrosion electrodes 12a and 12b, is to be zero or negative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine, and more particularly to a method and an apparatus for preventing a work from being rusted on a surface of a work left in a machining fluid after machining. About.

[0002]

2. Description of the Related Art A work that has been processed by a wire electric discharge machine generates rust on the surface of the work over time because the wire electric discharge machine uses water as a machining fluid. In particular, when the work is left in water for a long time, rust generation becomes more remarkable. FIG. 4 is an explanatory view of the electrochemical corrosion of the work in the working fluid. As shown in FIG. 4, the work to be used is usually carbon steel, and an infinite number of anodes and cathodes having different potentials are mixed on the surface of iron, which is a component thereof, and an infinite number of local batteries are formed. You. Oxidation and reduction are performed between the anode and the cathode of this local battery, and the iron cation F
e ²⁺ and Fe ³⁺ are precipitated and combine with the anion OH ⁻ in the working fluid using water to form a red rust iron hydroxide Fe.
(OH) ₂ and Fe (OH) ₃ are formed. This phenomenon is so-called electrochemical corrosion (electrolytic corrosion).

[0003] Japanese Patent No. 2547 discloses a technique for preventing the generation of rust on the surface of a work in a machining fluid due to electrolytic corrosion.
No. 365 (registration date August 8, 1996). The electric discharge machining power supply device of the invention described in the above patent publication is an electric discharge machining power supply device that performs electric discharge machining by applying a voltage with a predetermined polarity between both the machining electrode and the work electrode.
A first means for detecting an average voltage between the two electrodes; and a second means for applying a voltage having a polarity opposite to the predetermined polarity between the electrodes during a pause period of discharge by the voltage having the predetermined polarity.
Means, and the level of the voltage of the opposite polarity or the level and time of the voltage output from the second means according to the difference between the average voltage detected by the first means and a predetermined allowable value. A third means for controlling the length in a direction in which the average voltage becomes zero, and an open state in which no discharge occurs between the two electrodes even though the voltage of the predetermined polarity is applied for a predetermined time. A fourth means for detecting that the open state has continued, and an average value detected by the first means until the occurrence of discharge is detected when it is detected that the open state has continued for a predetermined time or more. Fifth means for alternately and repeatedly generating the voltage of the predetermined polarity and the voltage of the opposite polarity so that the voltage becomes zero and applying the voltage between the two electrodes is provided.

[0004]

However, the invention described in the above-mentioned patent publication prevents electric erosion of a work only during execution of a predetermined electric discharge machining step on the work, but after the electric discharge machining step is completed. Electric corrosion is not prevented for a workpiece left in the processing liquid during the suspension of processing. Therefore, there is a problem that rust is generated on the surface of the workpiece left in the processing liquid during the suspension of the processing.

Therefore, the present invention solves the above-mentioned problems, and provides a work rust prevention method and apparatus of a wire electric discharge machine for preventing rust from being generated on the surface of a work left in a machining liquid during machining suspension. The purpose is to provide.

[0006]

According to the present invention, there is provided a method for preventing rust of a workpiece in a wire electric discharge machine, which solves the above-mentioned problems. In a work rust prevention method of a wire electric discharge machine for performing machining, it is determined whether or not the electric discharge machining is paused, it is determined whether or not the work is in a machining fluid, and the electric discharge machining is suspended. Medium, and when it is determined that the work is present in the working fluid, an anticorrosion current is applied to the surface of the work so that metal ions of the work are not released into the working fluid. .

In the method for preventing rust of a work of a wire electric discharge machine according to the present invention, when it is determined that electric discharge machining is stopped and the work is present in the working fluid, metal ions of the work are released into the working fluid. A direct current is caused to flow into the metal surface of the work so as to prevent the local battery formed on the surface of the work from being eliminated due to the polarization action, and as a result, electrolytic corrosion of the work is prevented.

[0008] A work rust preventive device for a wire electric discharge machine according to the present invention which solves the above-mentioned problem is a wire electric discharge machine for machining a work by applying a voltage between a work in a machining fluid and a wire electrode to generate a discharge. In the work rust prevention device of the machine, a determination means for determining whether the processing is paused, and whether the work is in a processing liquid, an anticorrosion electrode installed in the processing liquid, and the determination means When the determination result is affirmative, a corrosion protection power supply that applies a voltage between the work and the anticorrosion electrode so that metal ions of the work are not released from the work into the working fluid is provided. And

A work rust prevention device for a wire electric discharge machine according to the present invention is provided with a work installed in a machining fluid by a corrosion protection power supply so that metal ions of the work are not released from the work installed in the machining fluid into the machining fluid. Since a voltage is applied between the electrode and the electrode, a direct current flows from the anticorrosion electrode to the metal surface of the work, and the anticorrosion action of eliminating the local battery formed on the work surface by the polarization action is obtained. Electrolytic corrosion is prevented.

In the work rust prevention apparatus for a wire electric discharge machine according to the present invention, the anticorrosion power supply applies a DC voltage between the work and the anticorrosion electrode, the work being a negative electrode and the anticorrosion electrode being a positive electrode. DC power supply. In another work rust prevention device for a wire electric discharge machine according to the present invention, the anticorrosion power supply is configured such that an average voltage applied between the work and the anticorrosion electrode is zero or negative on the work side. And an AC power supply for applying an AC voltage between the two.

In another aspect of the present invention, the anticorrosion power supply is a high-frequency AC power supply for applying a high-frequency AC voltage between the work and the anticorrosion electrode. By using a high-frequency AC power supply as the anti-corrosion power supply, if the average voltage between the work and the anti-corrosion electrode is zero or negative on the work side, even if a voltage with the work as the positive electrode is applied, metal ions are generated from the work because it is a short time even if the voltage is applied. Without
Before the metal ions are generated, the polarity of the applied voltage is switched, and the electrolytic corrosion of the work is prevented.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a view showing an embodiment of a work rust prevention device for a wire electric discharge machine according to the present invention. As shown in FIG. 1, a work rust prevention device of a wire electric discharge machine according to the present embodiment uses water as a working fluid, and a pulse voltage from a pulse power supply 4 between a work 1 and a wire electrode 2 in the working fluid. Is applied, and the work 1 is processed by electric discharge generated between the work 1 and the wire electrode 2.
The wire electrode 2 is configured to travel in a vertical direction from a supply reel (not shown) via a travel path having guide rollers between an upper head 6a and a lower head 6b. Up and down 2
A work table 3 that can be fed and displaced in a two-dimensional plane is disposed between the two heads 6a and 6b.
Is attached. Electric discharge machining between the work 1 and the wire electrode 2 is performed with an initial hole (small hole) or an end edge of the work formed in advance on the work 1 as a starting point of electric discharge machining.

The work 1 and the wire electrode 2 are both connected to a pulse power source 4 for electric discharge machining, and when they are opposed to each other via a minute gap, a discharge is generated between the gaps. Electric discharge machining is performed. The wire electrode 2 is provided with a power supply 2a near the electric discharge machining action portion.
The work 1 is also connected to the pulse power supply 4 via an appropriate conduction circuit. And
In the electric discharge machining process, the workpiece 1 is subjected to the feed control together with the work table 3 in a two-dimensional plane, so that the electric discharge machining proceeds along a desired trajectory and a product having a desired shape is machined from the workpiece 1. Has become.

The upper and lower heads 6a and 6b are respectively provided with jet nozzles 8a and 8b for supplying a machining fluid. The machining fluid supplied to the jet nozzles 8a is pumped from a cleaning fluid tank (not shown) by a pump. Via a pipe, the jet is supplied from above to the electric discharge machining section as a jet from the jet nozzle 8a. On the other hand, the processing liquid supplied to the jet nozzle 8b for supplying the processing liquid is pumped up from a cleaning liquid tank (not shown) by another pump, and is ejected from the processing liquid nozzle 8b via a piping of the pump. Is supplied from below toward the electric discharge machining action portion.

The jet nozzles 8a of the upper and lower heads 6a, 6b,
The tip of the nozzle 8b is formed as a circular machining fluid ejection part, and the wire electrode 2 is configured to pass through the center. The tips of the jet nozzles 8a and 8b usually have the workpiece 1 and the wire electrode 2
Work 1 as much as possible without interfering with relative displacement with
Is set in a state of being in close contact with the surface of the jet nozzle 8a,
8b, the jet of the machining liquid is sufficiently supplied to the gap of the machining trajectory, and liquid leakage from the gap between the tip of the jet nozzles 8a, 8b and the surface of the work 1 is minimized.
Then, the machining fluid is always supplied in a stable amount in the electric discharge machining action portion between the workpiece 1 and the wire electrode 2,
A function for controlling the working fluid supply operation by the two pumps is provided, and the working fluid pumped up by the two pumps from the cleaning fluid tank of the working fluid is jetted to the electric discharge machining action part under a set pressure.

In the above-described electric discharge machining process, as described in detail in the above-mentioned Japanese Patent Publication No. 2547365, the work 1 is controlled to be fed together with the work table 3 in a two-dimensional plane, and the pulse power supply 4 is controlled by the NC power supply. While receiving the processing command of the work 1 from the device 10, a positive or negative voltage is applied between the work 1 and the wire electrode 2 by the first power supply for processing the work 1 and preventing electrolytic corrosion. The second power supply supplies power to apply a negative or positive voltage having a polarity opposite to that of the first power supply.

On the other hand, according to the present invention, the prevention of electrolytic corrosion of the work during the machining suspension period is performed by applying a voltage from the anticorrosion power supply 14 between the work 1 and the anticorrosion electrodes 12a and 12b installed in the processing liquid. The applied voltage is controlled by the work 1 installed in the working fluid and the anticorrosive electrode 12 so that the metal ions Fe ²⁺ and Fe ³⁺ of the work 1 are not released from the work 1 into the working fluid.
a and 12b by applying a voltage from the following power supply. Here, the anticorrosion power supply and anticorrosion action according to the present invention will be described below.

FIG. 2 is an explanatory diagram of the anticorrosion action according to the present invention. As the first anti-corrosion power source, the work 1 is used as a negative electrode between the work 1 and the anti-corrosion electrode
A DC power supply that applies a DC voltage with 2a as a positive electrode can be used. Thereby, the anticorrosion electrode 12 is formed on the metal surface of the work 1.
A DC current flows from a to obtain an anticorrosion effect of extinguishing a local battery formed on the surface of the work 1 by a polarization action, thereby preventing electrolytic work of the work 1. In addition, the anticorrosion electrode 12
The material of a is preferably an insoluble material from which metal ions hardly fly out, for example, platinum. In the embodiment shown in FIG. 1, the anticorrosion electrodes 12a and 12b are arranged between the upper and lower heads 6a and 6b and the jet nozzles 8a and 8b. However, the anticorrosion electrodes may be provided at other positions or may be one. .

In another embodiment, instead of providing the anticorrosion electrode, a wire electrode 2 is used, and another power supply provided in the pulse power supply 4 is provided, and the work 1 is transferred from the work 1 into the machining fluid. A voltage can be applied between the work 1 immersed in the working fluid and the wire electrode 2 by the power supply so that the metal ions Fe ²⁺ and Fe ³⁺ are not released.

The second anti-corrosion power supply 14 is connected between the work 1 and the anti-corrosion electrodes 12a and 12b such that the average voltage applied between the work 1 and the anti-corrosion electrodes 12a and 12b is zero or negative on the work 1 side. An AC power supply that applies an AC voltage in between can be used. The application of the AC voltage causes a period in which a voltage having the work 1 as a positive electrode is applied between the work 1 and the anticorrosion electrodes 12a and 12b, and the average applied voltage between the two electrodes is zero or negative on the work side. In this case, the same anti-corrosion action as that of the DC power supply can be obtained, and the electrolytic corrosion of the work 1 can be prevented.

As the third anti-corrosion power supply 14, a high-frequency AC power supply of several KHz or more for applying a high-frequency AC voltage between the work 1 and the anti-corrosion electrodes 12a and 12b can be used. This is because even if a voltage having the work 1 as a positive electrode is applied between the work 1 and the anticorrosion electrodes 12a and 12b, no metal ions are generated from the work 1 in a short period of less than 1 msec, for example. If the polarity of the applied voltage is switched from the positive electrode to the negative electrode before the operation, the electrolytic corrosion of the work 1 can be prevented.
Therefore, if a high-frequency AC power supply of several KHz or more is used, the electrolytic corrosion of the work 1 can be prevented.

Next, switching between the operation of the pulse power supply during the electric discharge machining process and the operation of the anticorrosion power supply during the machining suspension period according to the present invention will be described below. FIG. 3 is a flowchart of a work rust prevention method for a wire electric discharge machine according to the present invention. First, in step S1, the anticorrosion power supply 14
For example, an EOB indicating that the machining block command has been completed is read from the machining program received from the NC device 10, and it is determined whether or not the electric discharge machining is suspended. If it is determined that the electric discharge machining is suspended, step S2 is performed. The process proceeds to step S4 when it is determined that the electric discharge machining is being performed. Step S4
Then, the above-described anticorrosion control at the time of the normal electric discharge machining is performed. The anticorrosion control at the time of the electric discharge machining is performed as follows while the work 1 is subjected to the feed control together with the work table 3 in a two-dimensional plane.

After receiving a block command for processing the work 1 from the NC device 10, the pulse power supply 4 supplies a first power supply between the work 1 and the wire electrode 2 to make the wire electrode positive or negative. Apply a polar voltage. Next, the pulse power supply 4 captures the start of discharge from a change in voltage between the work 1 and the wire electrode 2, and pauses after applying the voltage by the first power supply for the discharge time τON after the start of discharge. During the suspension period of the voltage application by the first power supply, that is, during the discharge suspension period τOFF, a voltage of the second polarity (the polarity opposite to the first polarity) that makes the wire electrode negative or positive is applied by the second power supply. The application of the voltage by the second power supply during the discharge suspension period is performed so that the average voltage between the work 1 and the wire electrode 2 becomes zero or negative on the work 1 side. On the other hand, in the open state in which no discharge is detected even after a predetermined time has elapsed after the voltage of the first polarity is applied between the work 1 and the wire electrode 2 by the first power supply, a period until the discharge is detected. , And the application of the voltage by the first power supply and the second power supply is alternately repeated. Also during this open state, the voltage level or duration of the supply voltage from the first power supply or the second power supply is controlled so that the average voltage between the work 1 and the wire electrode 2 is zero or negative on the work 1 side. I do. As described above, the anticorrosion control during the electric discharge machining is executed, and the electrolytic corrosion of the work during the electric discharge machining is prevented.

In step S2, it is determined whether or not the work 1 is in the machining liquid from the machining program sent from the NC unit 10 to the anticorrosion power supply 14, as in step S1.
If it is determined that the work 1 is in the machining fluid, the process proceeds to step S
The routine proceeds to step 3, and if it is determined that the work 1 is not in the machining liquid, the routine ends. In step S3, since it is determined that the electric discharge machining is paused and the work 1 is in the machining fluid, the work 1 is set in the machining fluid so that the metal ions of the work 1 are not released into the machining fluid. Between the work 1 and the anticorrosion electrodes 12a, 12b described above.
A voltage is applied from the anticorrosion power supply 14 of FIG.

[0025]

As described above, according to the method and apparatus for preventing rust in a wire electric discharge machine according to the present invention, a workpiece is left in a machining fluid while machining is suspended and is immersed in the machining fluid. In order to prevent the metal ions from being released, an anticorrosion current flows into the metal surface of the work immersed in the working fluid, and an anticorrosion action is obtained that eliminates a local battery formed on the work surface by polarization. As a result, electric corrosion of the work can be prevented, and generation of rust on the work surface can be prevented.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of a work rust prevention device for a wire electric discharge machine according to the present invention.

FIG. 2 is an explanatory diagram of an anticorrosion action according to the present invention.

FIG. 3 is a flowchart of a work rust prevention method for a wire electric discharge machine according to the present invention.

FIG. 4 is an explanatory diagram of electrochemical corrosion of a work in a working fluid.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Work 2 ... Wire electrode 4 ... Pulse power supply 6a, 6b ... Upper head, lower head 8a, 8b ... Upper nozzle, lower nozzle 10 ... NC device 12a, 12b ... Corrosion prevention electrode 14 ... Corrosion prevention power supply

Claims (5)

[Claims] 1. A work rust prevention method for a wire electric discharge machine, in which a work is processed by a discharge generated by applying a voltage between a work in a working fluid and a wire electrode, the work being stopped or not. It is determined whether or not the work is present in the working fluid. When it is determined that the working is at rest and the work is present in the working fluid, the metal ions of the work are determined. A rust prevention method for a wire electric discharge machine, wherein a corrosion preventing current is applied to the surface of the work so that the work is not released into the working fluid. 2. A work rust prevention device of a wire electric discharge machine for processing a workpiece by a discharge generated by applying a voltage between the workpiece and a wire electrode in a working fluid, wherein the processing is suspended. Determining means for determining whether or not the work is present in the working fluid; an anticorrosion electrode installed in the working fluid; and when the determination result of the determining means is affirmative, the work is moved into the working fluid from the work. An anticorrosion power source for applying a voltage between the work and the anticorrosion electrode so that metal ions of the work are not released. 3. The wire discharge according to claim 2, wherein the anticorrosion power supply is a DC power supply that applies a DC voltage between the work and the anticorrosion electrode, the work being a negative electrode and the anticorrosion electrode being a positive electrode. Work rust prevention equipment for processing machines. 4. An AC power supply for applying an AC voltage between the work and the anticorrosion electrode such that an average voltage applied between the work and the anticorrosion electrode is zero or negative on the work side. The work rust prevention device for a wire electric discharge machine according to claim 2, wherein 5. The work rust prevention device for a wire electric discharge machine according to claim 2, wherein the anticorrosion power supply is a high-frequency AC power supply that applies a high-frequency AC voltage between the work and the anticorrosion electrode.