JPH0691431A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To keep on normal discharge between a work and a tool electrode, and thereby enhance machining efficiency even in rough machining and precise machining by providing a discharge control means keeping particulate solids or particulate liquid which are dispersed in machining fluid filled in a gap between the work and the tool electrode, at density at the time of normal discharge. CONSTITUTION:A density control means such as a filter Fa is provided to keep particulate solids or particulate liquid which are dispersed in machining fluid filled in a gap between a work and a tool electrode, at density at the time of normal discharge. The density control means is equipped with a filter means 8 which is controlled to allow particulates to be removed based on the measured density of particulate solids or particulate liquid dispersed in machining fluid, and with a particulate applying means which applies and disperses particulates prepared in advance into machining fluid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention removes material of a work piece by applying a voltage between a tool electrode and a work piece, which are opposed to each other with a minute gap in a working liquid, to generate an electric discharge. The present invention relates to an electric discharge machine for machining.

[0002]

2. Description of the Related Art In an electric discharge machining apparatus, fine machining scraps in the machining fluid and suspended particles of pyrolytic carbon serve as nuclei for initiating an electric discharge, and provide a smooth rise to a normal electric discharge state and a uniform and normal electric discharge state. It is important to maintain.

That is, when the density of the machining waste in the machining fluid is excessive, abnormal discharge such as concentrated discharge occurs frequently, and when the density is too small, the tool electrode is brought too close to the workpiece to maintain the discharge. Further, short circuits frequently occur and the stability of the processing is impaired, and when the density of such fine particles in the processing liquid changes, the discharge gap length changes and the processing accuracy decreases.

The particle size of fine particles also affects the maintenance of normal discharge, and if particles with an excessively large size remain in the working fluid, it is difficult for them to flow in the working fluid or they tend to adhere to each other to form a bridge, resulting in abnormal discharge. And short circuits occur frequently, and the stability of processing is impaired. Further, if the particle size distribution of the fine particles in the processing liquid changes, the processing accuracy will decrease as in the case of the above density.

The conditions under which normal electrical discharge machining is maintained differ depending on the material of the workpiece, the shape of the electrode, the level of machining accuracy, etc., but as an example, the same electrode is used as a tool and the area of about 10 cm 2 or less is used. When a die-sinking electric discharge machining with a finished surface roughness of 10 μm Rmax or less is performed on a processed product, the processing liquid consisting of mineral oil contains fine particles of 10 μm or less in a volume ratio of 0.1 to 1%.

[0006] In the conventional electric discharge machining apparatus, fine particles such as machining chips and pyrolytic carbon in the machining fluid are removed by a filter device or a precipitation device. At this time, the density of the microparticles in the machining fluid is Since it is determined by the generation rate of particles by electrical discharge machining and the removal rate by the filter device, etc., processing is performed depending on the content of processing such as rough processing or precision processing (finishing processing), that is, the processing accuracy level and the operating state of the particle removal means such as the filter device The density of the fine particles in the liquid was changing. This also applies to the particle size distribution of the fine particles remaining in the working fluid, which is determined by the particle size distribution of the fine particles generated by electric discharge machining and the removal characteristics of the fine particle removing means such as a filter. It changed depending on the driving condition.

Further, the conventional electric discharge machine has no means for measuring the amount or particle size distribution of fine particles in the working liquid, and has no technical idea for controlling them.

After all, the conventional electric discharge machining apparatus is a technical idea regarding the machining liquid to remove and clean the microparticles anyway, and has means for intentionally controlling the density and particle size distribution of the microparticles in the machining liquid. There wasn't. Therefore, during processing, the density is excessively large, too small or too small, or particles having an excessively large size have an adverse effect on the processing accuracy.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides an electric discharge machine equipped with means for adjusting the density and particle size distribution of solid fine particles or liquid fine particles dispersed in a working fluid to maintain a normal discharge environment. It is an issue.

[0010]

The present invention relates to an electric discharge machine.
A means for controlling the density of solid fine particles or liquid fine particles dispersed in the working liquid that fills the gap between the tool electrode and the workpiece is provided. The density control means maintains the fine particles at the density at the time of normal discharge.

The density control means may include a filter device. The filter device is for removing fine particles and is operated based on the measured density of the fine particles.
The density control means may include a particle size distribution control means. The particle size distribution control means adjusts the particle size distribution of the fine particles in the working liquid.

The density control means may be provided with a fine particle adding means for adding and dispersing fine particles prepared in advance in the working liquid. The fine particle addition means increases or decreases the addition amount of the fine particles based on the measured density of the fine particles dispersed in the working liquid. The density control unit and / or the particle size distribution control unit may be configured to change the density and particle size distribution settings of the fine particles in the working liquid in response to the difference in the processing accuracy level.

[0013]

The density control means adjusts the density of the fine particles dispersed in the working fluid that fills the gap between the tool electrode and the workpiece so as not to be too high or too low, and maintains an environment for normal discharge. The particle size distribution control means removes oversized particles from the working fluid, adjusts the particle size distribution of particles necessary for sustaining the discharge, and maintains the environment for normal discharge. The means for adding fine particles supplies fine particles of appropriate size to the working liquid,
These are the core of the discharge. The configuration in which the setting of the density of fine particles and the setting of particle size distribution can be changed enables appropriate electric discharge machining according to the machining accuracy level.

[0014]

EXAMPLE FIG. 1 relates to the first example and shows only the circulating system of the working fluid. The electric discharge machine 1 includes an electric discharge tank 2,
The pollutant tank 3, the clean solution tank 4, the control device 5 and the setting device 6 are provided, the electric discharge machining tank 2 and the pollutant solution tank 3 are connected by the return path 7, and the pollutant solution tank 3 and the clean solution tank 4 are connected to the filter path 8 Connected by. The polluted liquid tank 3 is connected to the electric discharge machining tank 2 via the first supply path 9, and the clean liquid tank 4 is connected to the electric discharge machining tank 2 via the second supply path 10.

The filter path 8 is provided with a pump Pb and a filter Fa, with the pump Pb on the side of the polluted liquid tank 3.
The first supply path 9 includes the pump Pa and the first flow rate control valve 1.
1 is provided with the pump Pa on the side of the polluted liquid tank 3. Also,
The second supply path 10 includes a pump Pc and a second flow rate control valve 12 on the side of the pump Pc that is the cleaning liquid tank 4.
The opening degree of each of the first and second flow rate adjusting valves 11 and 12 is controlled by the control device 5.

The controller 5 is an ordinary numerical controller (NC).
Central processing unit (CPU), input / output circuit, read-only memory (ROM), temporary storage memory (RA)
M) and the flow control valves 11 and 12 are provided with servo drive circuits and the like. The setting device 6 and the pollution sensor 13 are attached to the control device 5. The setting device 6 inputs an allowable value of the particle density in the working fluid and sets it in the control device 5, and the input value is stored in the RAM.
Note that the allowable value of the particle density affects the discharge environment, such as the level of processing accuracy, the material of the work piece, the type of electrical discharge machining (die cutting, wire cutting, swing machining, or the use of jumping). It is experimentally determined according to the combination of various elements and the degree thereof.

The pollution sensor 13 is a sensor which is arranged in the machining fluid of the electric discharge machining tank 2 and converts the light transmittance into an electric signal, the output of which is inputted to the input / output circuit of the controller 5. This type of sensor can measure a small amount of fine particles in the working fluid by scattering light even when it is a liquid, and functions as a pollution degree sensor.

The RAM also reads the output of the pollution degree sensor 13 at predetermined intervals and converts the output into a fine particle density,
Further, a work program for comparing the density set by the setter 6 and adjusting the opening degrees of the first flow valve 11 and the second flow valve 12 based on the result is stored. In addition, even if the opening degree of the first and second flow valves 11 and 12 is adjusted to adjust the density, the work program
It is created so that the amount of machining liquid in the electric discharge machining tank 2 does not change.

The filter Fa is a cartridge type paper filter for trapping particles of 5 microns or more. The density and particle size distribution of the fine particles in the working liquid are adjusted as follows. First, the fine particle density corresponding to the level of processing accuracy is set by the setting device 6.

The electric discharge machine 1 is operated and the machining liquid is circulated along with the electric discharge machining. That is, the machining liquid in the electric discharge machining tank 2 is guided to the pollutant liquid tank 3 through the return path 7, and a part of the pollutant liquid tank 3 is directly pumped by the pump Pa via the first supply path 9 to the electric discharge machining tank 2 as it is. After being collected in the clean liquid tank 4 by the pump Pb via the filter path 8, the others are guided by the pump Pc to the electric discharge machining tank 2 via the second supply path 10. The processing liquid in the cleaning liquid tank 2 is
Since the filter Fa removes particles having an excessive size of 5 microns or more, and the clogging of the filter Fa also removes a part of the particles having a size of 5 microns or less, the density of fine particles is low.

Particles such as machining scraps and pyrolytic carbon increase in the machining fluid of the electric discharge machining tank 2 as the electric discharge machining progresses. When the density of fine particles in the machining fluid of the electric discharge machining tank 2 measured by the pollution sensor 13 becomes higher than the set value, the control device 5 reduces the opening degree of the flow rate control valve 11 of the first supply path 9, and accordingly, 2 The opening degree of the flow control valve 12 of the supply path 10 is increased. As a result, the supply amount of the cleaning liquid is increased and the density is lowered. On the contrary, when the density is increased, the opening degree of the flow rate control valve 12 is reduced, and the flow rate control valve 1 is correspondingly reduced.
Increase the opening of 1. In any case, the total amount of the machining fluid supplied to the electric discharge machining tank 2 is constant. Fine particles such as machining scraps and pyrolytic carbon generated by electric discharge machining
According to the ratio of the amount of processing liquid supplied to the first supply path and the second supply path 10, a certain ratio is removed by the filter Fa, so that the density of fine particles in the electric discharge machining tank 2 is determined.

In this way, the density and particle size distribution of the working fluid are adjusted. That is, the pollution sensor 13 is a means for measuring the density of fine particles in the working liquid, and is provided with the controller 5 having the setting device 6 and the pollution sensor 13 attached thereto, and the flow rate control valve 11 controlled by the controller 5. Second supply line 10 with line 9, filter line 8 and flow control valve 12 controlled by controller 5.
Is a density control means provided with a filter device for removing the fine particles by controlling based on the measured density of solid fine particles or liquid fine particles dispersed in the working liquid,
The processing liquid circulation path provided with the filter path 8 serves as a particle size distribution control means for fine particles.

Fine particles such as tar-like viscous oil particles are strained by the filter Fa like the pyrolytic carbon (soot). For an emulsion such as water, use an electrostatic filter.
A structure having a DC voltage of about 0 to 100 V) is used. A small amount of water emulsion is adsorbed and removed by a hydrophilic paper filter. With the above configuration,
Since the density of fine particles in the machining fluid in the electric discharge machining tank 2 is always feedback-controlled so as to be close to the set value, the electric discharge environment is normally maintained, and abnormal electric discharge, the work piece and the tool electrode, the work piece and the wire. A short circuit with the electrode is less likely to occur.

FIG. 2 relates to the second embodiment. Similar to the first embodiment, the electric discharge machining apparatus 1 includes an electric discharge machining tank 2, a pollution liquid tank 3, a cleaning liquid tank 4, a controller 5, a setting device 6, a pollution degree sensor 13, a return path 7, and a first supply. A path 9 and a second supply path 10 are provided, and a first flow rate control valve 11 and a second flow rate control valve 12 controlled by the controller 5 are provided in the first and second supply paths 9 and 10. ing.

However, in the second embodiment, the coarse filtrate tank 14 is arranged between the polluted liquid tank 3 and the clean liquid tank 4.
The coarse filtrate tank 14 is connected to the pollutant tank 3 via the first filter path 8a via the pump Pd and the pump Pb.
It is connected to the clean liquid tank 4 by the second filter path 8a via the. The filter Fb in the first filter path 8b is a coarse filter capable of trapping particles of about 10 microns or more, and the second filter path 8a.
The filter Fa in is a filter that traps particles of 5 microns or more. In addition, in this embodiment, the first supply path 9 via the pump Pa is connected to the coarse filtrate tank 14.

When the electric discharge machining apparatus 1 is operated, the machining liquid is circulated in the same manner as in the first embodiment, and the electric discharge machining tank 2 is provided with the first machining fluid.
And the second supply path 10 of the particle size 10
The coarse filtrate from which fine particles of micron or more have been removed and the cleaning liquid from which fine particles of 5 micron or more have been removed are returned. Since this coarse filtrate contains fine particles having a particle size of 10 microns or less, if the ratio of the flow rate of the coarse filtrate to the circulating amount of the machining liquid is increased, the particle size contained in the machining liquid in the electric discharge machining tank 2 is 10 microns or less. The density of the fine particles is increased. On the other hand, in the second filter path 8a, the filter Fa
Since some of the fine particles having a particle size of 5 microns or less are removed due to the clogging, when the ratio of the flow rate of the cleaning liquid to the circulating amount of the machining liquid is increased, the particle size of 10 microns included in the machining liquid in the electric discharge machining tank 2 is increased. The density of the following fine particles is reduced. Then, similarly to the case of the density control means of the first embodiment, the openings of the flow rate adjusting valves 11 and 12 are adjusted by the control device 5 so that the density of fine particles in the machining fluid in the electric discharge machining tank 2 becomes a set value. Controlled. In this case, since all the working fluid circulates via the first filter path 8b, all the excessive particles of 10 microns or more are removed from the working fluid supplied to the electric discharge machining tank 2. That is, the first filter path 8b constitutes a part of the particle size distribution control means.

In the second embodiment, the oversized particles in the machining fluid in the electric discharge machining tank 2 are generated only on the spot by electric discharge machining, and are extremely small, so that the environment for normal electric discharge can be adjusted more precisely. To be

FIG. 3 relates to the third embodiment. Similar to the first embodiment, the electric discharge machining apparatus 1 includes an electric discharge machining tank 2, a pollution liquid tank 3, a cleaning liquid tank 4, a controller 5, a setting device 6, a pollution degree sensor 13 arranged in the cleaning liquid tank 4, and a return. Although the filter path 8 is provided to connect the polluted liquid tank 3 and the cleaning liquid tank 4 via the path 7, the pump Pb, and the filter Fa, there is no path corresponding to the first supply path 9, and the cleaning liquid is supplied via the pump Pc. Second supply path 1 connecting the tank 4 to the electric discharge machining tank 2
Only have 0s.

A hopper 15 for accommodating fine particles for addition is provided above the clean liquid tank 4, and a stirring device 17 having a stirring blade 16 arranged in the clean liquid tank 4. The hopper 15 is provided with a flow rate control valve 18 at the discharge port, and the opening degree of the hopper 15 is controlled by the controller
Controlled by. The controller 5 converts the output of the pollution sensor 13 into the density of fine particles, compares this with the density value set by the setter 6, and opens the flow rate control valve 18 of the hopper 15 when the set value is low. A program for supplying a predetermined amount of the stored fine particles and controlling the measured density to be a set value is incorporated. That is, the hopper 15, which stores the fine particles for addition, the flow rate control valve 18, and the control device 5 which adjusts the opening degree thereof, constitute fine particle addition means.

The filter Fa captures particles having a size of 5 microns or more, and the additive particles contained in the hopper are alumina powder, silicon powder or graphite powder having a particle size of 1 to 5 microns.

When the electric discharge machining apparatus 1 is operated, the machining liquid is pumped from the electric discharge machining tank 2 through the return path 7, the contaminated liquid tank 3, the filter path 8, the cleaning liquid tank 4 and the supply path 10.
It circulates by b and Pc.

Normally, the working fluid circulates while maintaining the fine particle density necessary for maintaining normal discharge, but the amount of fine particles generated in finishing or precision machining is small,
Alternatively, the particle size of the fine particles generated by rough processing may be large and almost all may be captured by the filter. Further, the filter may be clogged to remove the fine particles more than necessary. In such a case, the control device 5 determines the decrease in the density of the machining fluid from the measured value of the pollution sensor 13, opens the flow rate control valve 18 of the hopper 15, and removes the fine particles inside the machining fluid of the electric discharge machining tank 2. Supply to. The supplied fine particles are uniformly dispersed by the stirrer 17.

As described above, the particle density of the machining liquid in the electric discharge machining tank 2 is adjusted, and the particle size distribution is determined by the particle size of the particles supplied from the filter Fa and the hopper 15. In this sense, the fine particle adding means constitutes a part of the particle size distribution controlling means.

In the first to third embodiments, the density set by the setting device 6 and the particle size of the fine particles captured by the filters Fa and Fb differ depending on the level of processing accuracy and the material of the workpiece. Appropriate values are selected for each.

The above is an embodiment, and the present invention is not limited to the illustrated specific configuration. For example, in the second embodiment, a third supply path that is directly supplied from the polluted liquid tank 3 to the electric discharge machining tank 2 via the third flow rate control valve is provided to make the density adjustment and particle size distribution adjustment more fine. It is also possible to do it. The particle size distribution control means may be composed of a centrifugal separator, an adsorber or a filter incorporated in the filter path 8 and a combination thereof.

Further, in the first embodiment, the return path 7
Also provided with a flow rate control valve controlled by the control device 5,
By adjusting the opening degree of this valve and the opening degrees of the flow rate adjusting valves 11 and 12 in the first and second supply paths, it is possible to adjust the total amount of supply and adjust the density and particle size distribution.

[0037]

[Effects of the Invention] In the electric discharge machine, the normal electric discharge is maintained between the work piece and the tool electrode, and the machining efficiency is good in rough machining and precision machining. it can.

[Brief description of drawings]

FIG. 1 is a mechanism diagram showing a circulating system of a working fluid (first embodiment).

FIG. 2 is a mechanism diagram showing a working fluid circulation system (second embodiment).

FIG. 3 is a mechanism diagram showing a working fluid circulation system (third embodiment).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electric discharge machine 2 Electric discharge tank 3 Contaminated liquid tank 4 Clean liquid tank 5 Control device 6 Setting device 7 Return path 8 Filter path 9 First supply path 10 Second supply path 11 First flow control valve 12 Second Flow control valve 13 Pollution sensor 14 Coarse filtrate tank 15 Hopper 16 Stirring blade 17 Stirrer 18 Flow control valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Yamaguchi 3580 Koshinoba, Oshinomura, Minamitsuru-gun, Yamanashi Prefecture FANUC CORPORATION (72) Inventor Shunichi Otaka 3580 Kobaba, Oshinomura, Minamitsuru-gun, Yamanashi Prefecture Local FANUC Co., Ltd.

Claims (6)

[Claims] 1. An apparatus for removing a material of a work piece by applying a voltage between a tool electrode and a work piece, which are opposed to each other with a minute gap in the working liquid, to generate a discharge. ,
An electric discharge machining apparatus comprising a density control means for maintaining the density of solid fine particles or liquid fine particles dispersed in a working liquid that fills a gap between a tool electrode and a work piece at a normal discharge. 2. The electric discharge machining apparatus according to claim 1, further comprising a particle size distribution control unit for adjusting a particle size distribution of solid fine particles or liquid fine particles dispersed in the working liquid, in addition to the density control unit. 3. The density control means comprises a filter device which is controlled based on the measured density of solid fine particles or liquid fine particles dispersed in the working liquid to remove the fine particles. The electric discharge machine according to claim 2. 4. The electric discharge machining according to claim 1, wherein the density control means includes a fine particle addition means for adding and dispersing fine particles prepared in advance in the working liquid. apparatus. 5. The fine particle adding means increases or decreases the addition amount of the fine particles based on the measured density of the solid fine particles or the liquid fine particles dispersed in the working liquid. 4. The electric discharge machine described in any one of 4. 6. The density control means and / or the particle size distribution control means changes the density of solid fine particles or liquid fine particles dispersed in the working liquid or the setting of the particle size distribution of these fine particles in response to the difference in the processing accuracy level. The electric discharge machining apparatus according to any one of claims 1 to 5, which is capable of being formed.