JPS61241022A - Electric discharge machining method - Google Patents

Abstract

PURPOSE:To prevent generation of a flame, by immersing a machining part in the water and supplying hydrocarbon, adding a surface-active agent, to a machining gap from an electrode constituting a machining load surface by a porous material. CONSTITUTION:A workpiece 6 is mounted onto a base bed 7 in a machining tank 5. A machining electrode 3, so that its part forming an electric discharge machining gap being mutually opposed to the workpiece 6 forms many fine holes on a machining load surface, is molded by a porous material 4 of carbon material and porous sintered material or the like, while the electrode provides inside a machining fluid feed path 3a. Machining fluid, fed from the machining fluid feed path 3a and consisting of kerosene, is supplied into the machining gap through the porous material 4. The machining fluid is separated into kerosene and water in a separably processing tank 18B. The kerosene is supplied to be jetted as necessary to a machining gap part from its peripheral machining fluid injection units 23, 24.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electric discharge machining method, and in particular, to a method for preventing unexpected disasters caused by the machining fluid when machining is performed using a flammable fluid as the machining fluid. The present invention relates to an electrical discharge machining method configured to enable the electrical discharge machining.

[Prior art and its problems]

In recent years, electric discharge machining machines have become widespread, and with the development of automatic control equipment, it has become possible to operate these electric discharge machining machines unattended for long periods of time.

Therefore, in the above-mentioned electrical discharge machining equipment, generally,
Machining is performed by placing the workpiece and the tool electrode facing each other and applying a voltage such as a voltage pulse between them. When performing the above machining, the workpiece is immersed in a machining liquid filled in a machining tank, or Machining is performed while constantly supplying machining fluid to the machining area by spraying or the like.

The most suitable processing fluid is kerosene, or a mineral oil-based fluid such as kerosene that contains some kind of additive to raise the ignition temperature, but this has the problem that it burns violently when ignited. Various nonflammable or N-flammable machining fluids have been proposed. However, it is currently not in practical use because it is inferior to kerosene in terms of processability.

As the above-mentioned machining fluid becomes contaminated during processing, and its concentration and temperature also need to be maintained at an appropriate level, the machining fluid in the machining tank must be collected and purified as appropriate. Depending on the case, the liquid may be adjusted in concentration and other liquid properties before being supplied to the processing gap or into the processing tank again. When using mineral oil-based flammable machining fluids such as the above-mentioned kerosene, electrodes,
It is necessary to perform machining while the machining gap between the workpieces is immersed in the machining liquid, so a float switch or other liquid level detector is installed in the machining tank to keep the liquid level in the tank constant at all times. In addition to controlling the tank to maintain the same level, the tank itself is also equipped with an overflow pipe, so that excess machining fluid is naturally drained from the tank.This prevents machining fluid from overflowing from the machining tank to the outside. It is now possible to prevent this from happening.

However, when the machining tank or workpiece is moved by numerical control during positioning or machining, the machining fluid in the machining tank may ripple and overflow outside the machining tank. The above float switch may malfunction, or the seal on the processing tank may not be perfect and the processing fluid may leak out in small amounts.In such cases, the processing fluid may be flammable such as kerosene. This may cause a fire, and carbon particles may be generated between the electrode and the workpiece even if there is no accident such as a ridge. When such carbon grains are generated, the discharge is concentrated in the part of the carbon grains and shifts to an abnormal discharge such as an arc. Therefore, in order to avoid this abnormal discharge, the electrode is automatically moved by the servo machining feed control device. The carbon grains are then pulled up a small distance, but this causes the carbon grains to grow further and develop into a long, box-like shape. When the tip of the carbon tray reaches the kerosene liquid level, the kerosene ignites due to electrical discharge, causing a large fire. Therefore, conventional float switches and other safety devices alone are not necessarily sufficient to prevent these unexpected accidents.

For this reason, for example, when a servo control device operates such that the electrode is pulled up a predetermined distance or more from a predetermined machining position, or when a servo control device operates such that the tip of the electrode is lifted above the level of the machining fluid in the machining tank. If a fire occurs, the system will detect this and turn off the power and stop electrical discharge machining, or if a fire still occurs, it will detect the occurrence of a fire based on light, temperature, etc. and activate a fire extinguisher that has been prepared in advance. There are also measures being taken to extinguish the fire.

However, on the other hand, it is not only possible that the electrical discharge machine becomes the source of a fire, but also that a fire that occurs elsewhere and its spread may ignite and make the fire bigger. The storage of a large amount of flammable mineral oil-based machining fluid in the machining fluid supply and treatment device and the machining tank, ie, the use of kerosene or the like as the machining fluid, is itself becoming a problem.

For this reason, for example, Japanese Patent Application Laid-open No. 51-128089,
No. 52-056491, No. 52-056492, No. 53-101197 and No. 56-163
A nonflammable aqueous processing fluid containing organic substances and other additives, but mostly water, as described in Japanese Patent Application No. 840, has been developed and is now being used in some areas.

However, this water-based machining fluid is suitable for various machining conditions such as rough machining, semi-machining, and finishing machining in wire cut electric discharge machining, etc., where the machining area of the machining gap where the electrode and the workpiece face each other is small. (Although it can be used, it has various problems when compared to the mineral oil-based machining fluid mentioned above in die-sinking machining where the machining area is larger than wire cut electric discharge machining etc.) However, many solutions have already been made by changing the type and amount of additives to water, the type of electrodes used, or even the processing method as described in JP-A-58-082630. However, for example, in the area of semi-finishing to finishing machining, it is possible to make electrode wear, machining speed, machining accuracy, machining stability, etc. comparable to that of conventional mineral oil machining fluids such as kerosene. That was difficult.

For this reason, for example, mineral oil-based machining fluids such as kerosene are added to the machining gap in water or a fluid containing water as a main component as described in JP-A-58-010428 and JP-A-5B-077410. A method of electrical discharge machining by supplying kerosene, etc., has been proposed, but although the amount of kerosene, etc. stored in this method is small, mineral oil such as kerosene, etc. that floats on the upper surface of the liquid in the machining section or the machining tank section has been proposed. There were various problems with the recovery of the waste, and it was not possible to say for certain that there was no possibility of a fire occurring.

[Object of the present invention]

The present invention was made to solve the problem of ridges, and its purpose is to substantially use conventional hydrocarbon mineral oil such as kerosene as the machining fluid during machining, and to When it is discharged from the machining gap, it is immediately mixed with water stored in the machining tank and mixed with a surfactant if necessary, and the used machining fluid is safely recovered. It is an object of the present invention to provide an electric discharge machining method that prevents the occurrence of the above-mentioned accidents and also enables long-term unmanned machining.

[Means for solving problems]

The above purpose is to store a workpiece in a processing tank, to make the workpiece and an electrode face each other with a predetermined distance therebetween, and to apply voltage pulses between the two to process the workpiece. In the electric discharge machining method, the machining tank is filled with water or water mixed with a surfactant as necessary, and the electrode and the opposing machining part of the workpiece are immersed in the water in the machining tank. In this state, as the electrode, at least the machining load surface is made of a porous material and is provided with a machining fluid supply path for supplying machining fluid to the porous portion, and as the machining fluid, a surfactant is used. This is supplied to the machining gap through the machining fluid supply path and porous portion of the electrode, and the machining fluid flowing out from the machining gap and other parts is mixed with the water in the machining tank for machining. This is achieved by doing the following.

[For production]

If the processing is carried out as described above, kerosene with good processability can be used as the processing fluid, and since kerosene is only mixed in the water at a low concentration in the processing tank, virtually no fire will occur. There is no danger, and even if a fire were to occur, the amount of stored hydrocarbons is extremely small compared to conventional methods, so it would only be a small fire, and there would be no possibility of the fire spreading, minimizing damage. This enables long-term unmanned processing.

Of course, in order to achieve the above purpose, it is necessary to have a sufficiently large amount of water or surfactant-added water in the processing tank in which the electrode and the workpiece are installed, in other words, the surfactant that is sprayed into the processing gap. New water is supplied in an amount that is hundreds to thousands of times more than the amount of added oil, and that the water in the processing tank is always sufficiently larger than the amount of oil that is supplied into the processing gap. It is necessary for continuous machining to continue for a long time.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to embodiments shown in the drawings.

FIG. 1 is an explanatory diagram showing one embodiment of the electric discharge machining apparatus according to the present invention, FIG. 2 is an explanatory diagram showing another embodiment of the machining electrode part, and FIG. 3 is an explanatory diagram showing another embodiment of the electric discharge machining apparatus according to the present invention. FIG.

First, the explanation will be given with reference to FIG.

In Fig. 1, 1 is the machining machine body of the electric discharge machining device, 2 is the machining head, and 3 is molded with a porous body 4 such as a porous sintered body so that many micropores are formed in the lower part. 5 is a processing tank, 5a is a sub-tank, 6 is a workpiece, and 7 is a base on which the workpiece 6 is mounted. , 8.9
．． 10.11 and 12 are solenoid valves, 13.14.15.1
6 and 17 are pumps, 18 is a processing tank for supplying processing fluid, etc.
18A is petroleum or, for example, non-ionic, preferably 100
18B is a processing liquid storage tank made of petroleum to which a desired amount of surfactant (approximately several percent) is added, and 18C is a processing liquid tank containing water or surfactant. A storage tank that stores water to which a desired amount of approximately several percent has been added;
19 is a heating or cooling device for the stored liquids 18A, 18B and 18C; 20. 21 and 22 are filters; and 24 is a device for spraying kerosene into the processing gap formed by the processing electrode 3 and the workpiece 6. A machining fluid injection device and a section for supplying the machining fluid are provided in the machining tank 5 and sub-tank 5.
A partition plate 25a defining a is a hole formed in the partition plate portion.

The workpiece 6 is mounted on a base 7 in the processing tank 5, and is moved in the X-axis direction and the Y-axis direction by a cross slide table (not shown) on which the processing tank 5 is mounted. A positioning movement or a machining feed movement is provided.

The electrical discharge machine main body 1 itself is almost the same as a known electrical discharge machine, but the part of the machining electrode 3 that faces the workpiece 6 and forms the electrical discharge machining gap has a large number of microscopic particles on the machining load surface. The electrode is molded with a porous body 4 such as a carbon material or a porous sintered body so that holes are formed therein, and a machining fluid supply channel 3a is provided inside the electrode.
is provided.

Thus, the machining fluid made of kerosene or surfactant-containing kerosene supplied from the machining fluid supply path 3a is supplied to the gap between machining via the porous body 4.

In the processing liquid separation treatment tank 18B, a mixture of kerosene, water, and surfactant is heated to below cloudy temperature, and the surfactant is separated by adhering to mixed powder (iron powder) and precipitating, and the kerosene is separated by water in the upper layer. is separated into lower layers.

Then, the kerosene collected in the machining fluid storage tank 18A is mixed with a surfactant as required, passes through the pump 16, the filter 22, and the solenoid valve 11, and is passed through the machining fluid supply path 3a of the machining electrode 3 through the porous hole. It is supplied to the machining gap formed by the machining electrode 3 and the workpiece 6 through the machining load surface formed by the mass body 4 .

Further, if necessary, kerosene or kerosene to which a surfactant has been added is sprayed and supplied from the machining fluid spraying device 24 to the machining gap portion from around the machining gap portion. The machining fluid jetted and supplied from the machining fluid supply path 3a to the machining gap through the gap in the porous body 4 and the machining fluid jetted and supplied to the machining gap via the machining fluid injection device 24 are transferred to the machining tank. It is mixed with water stored in the container 5 or water to which a surfactant has been added.

It is recommended that the machining fluid, such as kerosene, be sprayed and supplied to the machining gap by the machining fluid spraying device 24 so as to cover the entire surface of the machining electrode 3. Note that finishing can be effectively performed by setting the ejection pressure to about 3 atm or less.

The machining electrode 3 and the workpiece 6 are opposed to each other with a predetermined machining gap maintained, and a machining voltage pulse is applied between them from a machining power supply device (not shown). and a machining fluid injection device ejects a machining fluid made of petroleum or the like mixed with kerosene or a surfactant from 24 to generate electrical discharge in the machining gap, and machining the workpiece 6 by the discharge erosion. A processed shape corresponding to the shape of the electrode 3 is etched.

During machining, the machining fluid is supplied to the supply processing tank 18 as described above.
The machining fluid storage tank passes through the pump 16, the filter 22, and the solenoid valve 11, and is jetted and supplied from the machining fluid supply path 3a of the machining electrode 3 to the machining gap via the porous body 4, and
From pump 14, 15 to filter 20, 21 to solenoid valve 9
．． The machining fluid passes through the machining fluid injection device 24 and is sprayed and supplied to the machining gap.

Machining fluid made of petroleum mixed with kerosene or surfactant contaminated with machining debris or altered by electrical discharge,
It is melted or suspended in the water in the processing tank 4 or water containing a surfactant, and the upper part of the suspension overflows due to the supply of processing liquid to the processing section and the supply of water, etc. to the processing tank 5, and the partition It passes through the hole 25a formed in the plate 5, enters the sub-tank 5a, and is collected in the separation treatment tank 18B.

Kerosene, water, and surfactant are recovered together in the separation treatment tank 18B, and when this is heated by the heating device 19 to a temperature higher than a certain temperature of the mixed surfactant, which is higher than cloudy temperature, the surfactant is As the agent separates from water and kerosene and coagulates and precipitates, or adsorbs to adsorbed materials such as iron powder and precipitates, the remaining water and kerosene separate into the original kerosene and water, and the above kerosene Since it is lighter than water, processing liquid storage tank 1
8A and water are collected in a storage tank 18G, and the surfactant is also collected and mixed with the oil and water in the storage tanks 18A and 18C in the required amount together with a new surfactant prepared separately.

The kerosene recovered in the processing liquid storage tank 18 is subjected to liquid quality control such as filtration and addition of the surfactant using a known device (not shown) to maintain a constant liquid quality at all times. . Then, the petroleum added with the kerosene or surfactant is supplied from the machining fluid supply path 3a formed in the machining electrode 3 to the gap between the porous body 4 and the machining fluid injection device.
After the machining electrode 3 and the workpiece 6 face each other and are ejected and supplied to a minute machining gap formed, electrical discharge machining is performed within the machining gap, and machining debris etc. generated by the electrical discharge machining are The machining fluid contaminated with this material is removed from the machining gap as much as possible and is always replaced with clean machining fluid. This also applies to the water stored and collected in the storage tank 18C or the water mixed with surfactant, and this water is constantly supplied into the processing tank 5 by the pump 17 through the valve 12 during processing. It is something that

Next, FIGS. 2 and 3 will be explained.

In Figures 2 and 3, the same numbers as those in Figure 1 indicate the same components, and 26.2
7 is a processing electrode, and 26a and 2'7a are the processing electrodes 2.
6. Nail machining fluid supply path, 2'? b is a machining liquid spout hole of the machining electrode nail.

Similarly to the machining electrode 3 of the electrical discharge machining device shown in FIG. 1, the machining electrode 26 shown in FIG. It is composed of a body 4. Approximately half of the petroleum to which kerosene or a surfactant has been added oozes out through the gaps in the porous sintered body 4 and is supplied to the processing gap, and the other half of the kerosene or kerosene to which a surfactant has been added is processed. Liquid supply path 2
Since it is directly supplied to the machining gap via 6a,
Since the machining fluid such as kerosene is sufficiently and evenly supplied to the machining gap, machining can proceed more smoothly.

In addition, in the case shown in FIG. 3, the entire machining electrode is made of the same material, and a large number of machining fluids such as kerosene are sprayed onto the part facing the workpiece 6. It has jet holes 2'7b and 27b formed therein.

Since the machining electrode nail can be integrally molded during manufacture, it can be manufactured at a lower cost than the machining electrodes shown in FIGS. 1 and 2.

〔Effect of the invention〕

Since the present invention is structured like a ridge, in accordance with the present invention, a conventionally used hydrocarbon oil such as kerosene is substantially used as the machining fluid, and when it is discharged from the machining gap, it is immediately removed. Processing is carried out by mixing with the water in the processing tank or water to which surfactants have been added, and the used flammable processing fluid is safely recovered in a non-flammable state, preventing accidents from occurring, and This makes long-term unattended processing possible. Furthermore, even if an unexpected accident occurs, only a small amount of machining fluid in the machining fluid storage tank 18A burns, so damage caused by fire can be minimized.

Note that the configuration of the present invention is not limited to the embodiment on the ridge. That is, for example, in this embodiment, kerosene or kerosene to which a surfactant has been added was used as the machining fluid, but other machining fluids made of known hydrocarbon mineral oils may be used. In addition, one machining fluid spray device was installed on each side of the machining electrode, and the machining fluid was injected into the machining gap from the machining fluid spray device. It can be increased or decreased as appropriate depending on the situation. Furthermore, the filters 20, 21, n may be provided between the sub-tank 5a and the processing tank 5 and the separation treatment tank 18B. It is recommended that the processing tank 5 be constructed so that water constantly overflows from the hole 25a of the partition plate 5 in order to prevent the concentration of dissolved flammable substances such as kerosene from increasing. In addition, in order to gradually supply kerosene from the machining electrode to the machining gap, the tip of the machining electrode was formed of a porous sintered body, etc., but other materials may be used as long as they can achieve the same effect. Known members can be used. In addition, the shape of the machining electrode, the method of supplying and recovering the machining fluid, etc. can be freely changed within the scope of the purpose of the present invention, and the present invention encompasses all of these.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing one embodiment of the electrical discharge machining apparatus according to the present invention, FIG. 2 is an explanatory diagram showing an embodiment of the pond in the machining electrode part, and FIG. 3 is an explanatory diagram showing another embodiment of the electric discharge machining apparatus according to the present invention. FIG.

Claims (1)

[Claims] 1) A workpiece is housed in a processing tank, the workpiece and an electrode are faced to each other with a predetermined distance maintained, and a voltage pulse is applied between them to perform processing. In the electric discharge machining method, the machining tank is filled with water so as to maintain the machining area between the electrode and the workpiece in an immersed state, and at least the machining load surface of the electrode is made of a porous material, and In addition to using an electrode provided with a machining fluid supply path for supplying machining fluid to the porous portion, a hydrocarbon to which a surfactant has been added is used as the machining fluid, and this is applied to the machining fluid supply path and the porous portion of the electrode. The electric discharge machining method described above is characterized in that machining is performed while the machining liquid is supplied to the machining gap through the machining gap and flowing out from the machining gap and other parts and mixed with water in the machining tank. 2) The electric discharge machining method according to claim 1, wherein the water stored in the machining tank is water mixed with a surfactant.