JP2841096B2 - Method and apparatus for treating EDM - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for treating water or an electric discharge machining fluid containing water.

(Prior Art) Conventionally, as a machining fluid for electric discharge machining, water or a so-called water-based machining fluid containing water has been widely used. When performing electric discharge machining using such a machining fluid, it is required to maintain the electric conductivity of the machining fluid within a predetermined range according to the purpose of machining. Conventionally, the increase in electrical conductivity during processing is due to metal ions generated by the processing of the electrodes and workpiece chips from the reaction with water and carbon dioxide gas dissolved from the air into the liquid. It was supposed to be.

Therefore, in order to remove these, a method has been generally adopted in which a working fluid is passed through a mixture of a cation exchange resin and an anion exchange resin to maintain the electrical conductivity of the working fluid at a required level. Was.

According to this conventional method, since a large amount of expensive ion exchange resin is required, there is a problem that the processing cost of the working fluid becomes extremely high.

In order to solve this problem, for example, Japanese Patent Application Laid-Open No. 57-201135
In the publication, by adding copper hydroxide powder to the working fluid, it is possible to prevent copper bicarbonate from being generated in the working fluid, thereby maintaining the specific resistance value of the working fluid at a predetermined value or more. A method of doing so is disclosed.

(Problems to be solved by the invention) However, in the method of attaching copper hydroxide powder in the working fluid,
Impurities are easily mixed into the working fluid, and it is extremely difficult to control the amount of addition to match the state of the working fluid. If copper hydroxide powder is excessively added, the processing accuracy is reduced. Has the problem of causing

An object of the present invention is therefore to provide an improved method and apparatus for processing a machining fluid, which can solve the above-mentioned problems in the prior art.

(Means for Solving the Problems) As a result of earnest studies, the present inventor has found that the increase in electric conductivity is not due to metal ions but to carbon dioxide gas dissolved from the air. It has been found to prevent an increase in conductivity. Therefore, in the method of the present invention, the required metal is disposed in the electric discharge machining fluid to be treated, and a positive potential is applied to the metal plate, so that the metal cation is electrochemically formed in the electric machining fluid. It is characterized in that it is eluted, thereby lowering the electric conductivity of the electric discharge machining liquid.

Further, the feature of the electric discharge machining liquid processing apparatus according to the present invention is that, in the processing apparatus for reducing the electric conductivity of water or the electric discharge machining liquid containing water, the electric discharge machining liquid is formed of a required metal disposed in the electric discharge machining liquid. A first electrode, a second electrode opposed to the first electrode at an interval in the electric discharge machining fluid, and a voltage for eluting cations from the first electrode into the electric discharge machining fluid. It comprises a voltage applying means for applying a voltage between the first electrode and the second electrode.

In the above configuration, the material of the metal electrode for eluting cations is, for example, magnesium, tin,
An appropriate metal other than an alkali metal, such as aluminum, zinc, copper, and iron, can be used. On the other hand, the electrode facing this may be any as long as it is made of a conductive material.

(Action) When a positive potential is applied to a required metal electrode in water or an EDM containing water, cations are eluted into the EDM by an electrochemical action. These cations react with carbonate ions and bicarbonate ions in the working fluid to be solidified, and can be removed by a filter. Therefore, carbonate ions, bicarbonate ions, and the like that cause an increase in the electrical conductivity of the working fluid can be removed without using an ion exchange resin. The amount of cations eluted from the metal electrode can be controlled, for example, by adjusting the level of the voltage applied between both electrodes.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

A machining fluid treatment device 1 shown in FIG. 1 is a device for treating water or a water-based machining fluid 3 used for electric discharge machining in a service tank 2, and includes a pump 4 and a filter 5, and includes a machining fluid. A filtration device 6 for separating solid impurities, such as, from the working fluid 3 is provided.

In this embodiment, the working fluid 3 is water, and the working fluid processing apparatus 1 further includes an electrical conductivity control device 7 for maintaining the electrical conductivity of the working fluid 3 at a predetermined level or less.

This electric conduction control device 7 dissolves carbon dioxide gas in the air in the machining fluid 3 or dissolves carbon dioxide gas generated by decomposition due to heat when the machining fluid 3 is used for electric discharge machining. For this reason, attention is paid to the fact that the electrical conductivity is increased by the carbonate ions and bicarbonate ions generated in the working fluid 3, and an appropriate amount of metal cation which reacts with these carbonate ions and bicarbonate ions to solidify them. In the working fluid, thereby controlling the electrical conductivity of the working fluid 3. The first electrode 8 made of a zinc plate and acting as a positive electrode
And second electrodes 9a and 9b serving as negative electrodes. The first electrode 8 has a size of 180 (mm) × 180 (mm) and a thickness of 1
(Mm) zinc plate is used as it is, and the second electrodes 9a, 9b
Are each configured as a stainless steel plate having the same dimensions as the first electrode 8. The first electrode 8 is opposed to the second electrodes 9a and 9b at a predetermined interval as shown in the drawing, and these electrodes are supported by a support member (not shown).
It is arranged in.

The first electrode 8 is directly connected to the positive electrode of the DC power supply 10, while the second electrodes 9a and 9b are connected in common and connected to the DC power supply 10 via the open / close switch 11 to the negative electrode. Therefore, when the open / close switch 11 is closed, the first electrode 8 made of zinc has a positive potential with respect to the second electrodes 9a and 9b, and zinc ions elute from the first electrode 8 into the working fluid 3. .

An output signal from a sensor 12 for detecting the electrical conductivity of the working fluid 3 for performing on / off control of the on / off switch 11 so that the elution amount of zinc ions is an appropriate amount for obtaining a required electrical conductivity. A detection circuit 13 that outputs a detection signal Sa indicating the electric conductivity of the working fluid 3 in response to D is provided. Reference numeral 14 denotes a setting device for setting the value of the target electric conductivity of the working fluid 3. The setting signal 14 outputs a setting signal Ss indicating the set electric conductivity, and the setting signal Ss
Is input to the determination unit 15 to which the detection signal Sa is input.

The discrimination unit 15 responds to both input signals Sa and Ss, performs a magnitude discrimination between the electric conductivity Cs set by the setting unit 41 and the actually detected electric conductivity Ca, and a discrimination signal indicating the discrimination result. B is output from the determination unit 15 and input to the switch control unit 16.

The switch control unit 16 responds to the determination signal B,
A switch control signal SC for controlling ON / OFF of the open / close switch 11 is output so that the open / close switch 11 is closed when> Cs, and is opened when Ca <Cs.

According to the above-described configuration, for some reason, the carbonate ions and bicarbonate ions in the working fluid 3 increase, the electrical conductivity of the working fluid 3 increases, and it is determined that Ca> Cs.
When the determination is made at 15, the on / off switch 11 is closed by the switch control signal SC output from the switch control unit 16. As a result, the first electrode 8 has a positive potential with respect to the second electrodes 9a and 9b, and zinc ions start to elute into the working fluid 3 from the first electrode 8, whereby the carbonate ions and the Bicarbonate ions react with zinc ions to form solidified zinc carbonate, which settles in the service tank 2.

In this way, carbonate ions and bicarbonate ions, which are one of the main causes for increasing the electrical conductivity of the working fluid 3, react with zinc ions to form zinc carbonate, and are filtered from the working fluid 3 by the filtration device 6. It is taken out separately.

As a result, the electric conductivity of the working fluid 3 can be easily and efficiently reduced without using an expensive ion exchange resin.

When the electrical conductivity of the working fluid 3 decreases and reaches a predetermined level, the open / close switch 11 is opened, and the elution of zinc ions is stopped.

Since the stainless steel plate used as the second electrode does not change due to energization, the second electrode can be used semi-permanently. The second electrode can be made of an appropriate material made of a conductive material, and the material is not limited to stainless steel.

In the above embodiment, an example in which a zinc plate is used as the material of the first electrode is shown. However, the material of the first electrode is not limited to this, and solidifies by reacting with carbonate ions and bicarbonate ions. Any metal material can be used as long as it can obtain a metal cation for causing the metal cation, for example, a metal such as tin, copper, iron, aluminum, and magnesium can be used. Can be obtained.

In the configuration shown in FIG. 1, since the amount of metal cation corresponding to the electric energy applied between the first and second electrodes is eluted into the working fluid 3, it is extremely easy to control the amount of metal cation eluted. It is very easy to control the cations so as not to be excessively eluted in the working liquid 3.

FIG. 2 shows experimental data showing the effect of the present invention. In this experimental data, 19 [μs / cm] of water was used as a working fluid, and the apparatus shown in FIG. 1 was left for 8 hours with the open / close switch 11 kept open. During this time, 5 V was applied between the first and second electrodes. The characteristic line (A) shows how the electrical conductivity of the working fluid 3 changes when a current of 0.04 (A) flows when a DC voltage is applied. The numbers shown in the graph indicate the amount [ppm] of carbon dioxide gas dissolved in the working fluid at that time, and the increase in electrical conductivity is suppressed over time. It can be seen that the increase in the amount of carbon dioxide in the liquid is suppressed. On the other hand, the result shown by the characteristic line (B) indicates a change in the electrical conductivity when the open / close switch 11 is kept open and only the filtration device 6 is operated. In this case, it can be seen that the concentration of carbon dioxide in the working fluid increases with the passage of time, and the electric conductivity also increases.

FIG. 3 shows the results of an experiment conducted under the same conditions as in FIG. 2 using a tin plate as the material of the first electrode. The characteristic line (C) shows the case where the tin ions are eluted, and the characteristic line (D) shows the case where the working fluid is simply circulated. In the case of FIG. 3 as well, the numbers shown in the graph indicate the amount of carbon dioxide gas [ppm] dissolved in the working fluid at that time.
It shows.

In both cases of FIGS. 2 and 3, the effect of eluting metal cations into the working fluid is clearly shown. The effect of lowering electrical conductivity by eluting metal cations can be expected for all working fluids containing water.

(Effects of the Invention) According to the present invention, as described above, metal cations are electrochemically eluted into water or a working fluid containing water using a metal electrode, thereby causing cations of the metal in the working fluid. The carbonate and bicarbonate ions generated by the solidification can be solidified and removed, so that the appropriate cations can be eluted into the working fluid very easily by simply applying a voltage, and the metal can be dissolved even by prolonged operation. The electrode has a small weight loss, and the metal electrode serving as the metal cation supply source does not need to be replaced frequently. This has the advantage that maintenance and inspection are simplified. Further, since an ion exchange resin is not required, there is also an effect that cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a working fluid processing apparatus according to the present invention, and FIGS. 2 and 3 are graphs showing experimental results of working fluid processing according to the present invention, respectively. 1 ... processing fluid treatment device, 2 ... service tank, 3 ...
Working fluid, 7 ... electric conductivity control device, 8 ... first electrode,
9a, 9b: second electrode, 10: DC power supply, 11: open / close switch.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-191514 (JP, A) JP-A-62-226099 (JP, A) JP-A-3-154713 (JP, A) Really open 105527 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23H 1/10, 7/36 G21D 1/00

Claims (3)

(57) [Claims] In a treatment method for removing ions in water or an electric discharge machining fluid containing water, a required metal plate is disposed in the electric discharge machining fluid to be treated, and a positive potential is applied to the metal plate. A method for treating an electric discharge machining liquid, characterized in that the metal cations are electrochemically eluted into the electric discharge machining liquid by applying, thereby reducing the electric conductivity of the electric discharge machining liquid. 2. A processing apparatus for lowering the electrical conductivity of water or an electric discharge machining fluid containing water, comprising: a first electrode made of a required metal disposed in the electric discharge machining fluid; And a second electrode that is disposed opposite to and spaced from the electric discharge machining fluid at an interval, and applies a voltage for eluting cations from the first electrode into the electric discharge machining fluid with the first electrode and the second electrode. And a voltage applying means for applying a voltage between them. 3. A detecting means for detecting the electric conductivity of the electric discharge machining fluid, a setting means for setting a required electric conductivity value of the machining fluid, and a means for responding to the detecting means and the setting means, 3. The apparatus according to claim 2, further comprising means for controlling application of a voltage by said voltage applying means so as to obtain a required electric conductivity.