JPH05285733A - Electric discharge machining method and its device - Google Patents

Abstract

PURPOSE:To provide an electric discharge machining method and its device which can achieve spice saving, and facilitates a reuse of powder in electric discharge machining which performs mirror surface machining with powder mixed with machining fluid. CONSTITUTION:In machining steps other than mirror finish machining, electric discharge finishing is performed while machining fluid is being circulated between a processing tank 1 and a machining fluid tank 2. In a mirror finish machining, powder is supplied to a processing tank 1 form a hopper 6 from which powder is supplied and supplemented, and a powder stocker 9, electric discharge machining is performed while powder is being stirred together with machining fluid by means of a stirrer 19 provided for the processing tank 1. After mirror finish machining has been over, machining fluid in the processing tank is pumped up into the powder stocker 9 to recover powder. The powder stocker 9 which is formed into a hermetic container, comprises an elastic member 18 housed in a filter cloth 16 which comprises a filter film formed in a bag shape inside, which allows machining fluid to pass through when powder is recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for performing electric discharge machining by supplying a powder into a working fluid in the final stage finishing such as finishing.

[0002]

2. Description of the Related Art In electrical discharge machining, usually, machining conditions such as voltage pulse and the like are switched from rough machining to finishing machining, and machining is carried out in several stages while electrode replacement is performed as necessary. Although it is performed separately, the finishing process of obtaining a particularly smooth and smooth surface as the final step is called a mirror finishing process. In such a mirror finishing process, the working fluid should be 0.1 μm to
By mixing a powder having a particle diameter of several tens of μm and made of, for example, silicon, and allowing the powder to flow through the processing gap,
It is known that dispersion of electric discharge is promoted, stable electric discharge machining can be performed, and surface roughness is improved. As one of them, Japanese Patent Application Laid-Open No. 3-277421 discloses an example in which a working liquid tank dedicated to powder mixing is provided in addition to a working liquid tank for conventional normal working such as rough working.

However, according to this structure, there is a problem that an extra space is required for installing the working fluid tank for exclusive use of powder mixing. Further, since the powder is filtered together with the processing waste through the filter, it is difficult to collect the powder from the filter and reuse it.

Further, since the working fluid tank is separately installed, there is a problem that the powder tends to settle in the working fluid tank, the pipe and the cooler, and the amount of the mixed powder tends to fluctuate.

In view of the above problems, the present invention achieves space saving and reuse of powder in an apparatus provided with an electric discharge machining means for mixing a powder into a machining fluid to perform mirror finishing. An object of the present invention is to provide an electric discharge machining method and an apparatus which facilitates the electric discharge machining.

[0006]

In order to achieve the above object, the electric discharge machining method of the present invention circulates a machining fluid between a machining tank and a machining fluid tank in a machining step other than final finishing. While performing electric discharge machining, in mirror finishing, powder is supplied into the processing tank from the hopper and powder stocker that supply or replenish the powder, and the powder is stirred with the processing liquid by the stirrer installed in the processing tank. It is characterized in that electric discharge machining is performed, and when the mirror finishing is completed, the working fluid is pumped up from the working tank into the powder stocker to collect the powder. When carrying out this electric discharge machining, as the agitator, a stirrer is optionally attached and an impeller for forming a jet-like jet flow is used, and the agitator is used to disperse almost all the area in the machining tank. It is more preferable to perform mirror finishing in a state where a flow is caused to flow and the powder is interposed in the processing gap.

Further, the electric discharge machining apparatus according to the present invention is installed separately from the machining fluid tank, and the powder storage hopper for supplying or replenishing the powder to the machining vessel and the machining fluid in the machining vessel are pumped up to collect the powder. A powder stocker with a recovery pump and a stirrer installed in the processing tank and stirring and mixing the processing liquid and the powder in the processing tank are provided, and the powder stocker has a closed container shape, An elastic member is housed inside a filter cloth having a bag-shaped filter membrane that allows the working fluid to pass through during powder recovery, and the working fluid is circulated from the outside to the inside of the filter cloth during powder recovery. The elastic member is contracted by the pressure difference between the inside and the outside, and when the flow of the working liquid is stopped, the elastic member is extended and the powder adhering to the filter cloth is detached.

Further, in the electric discharge machining apparatus of the present invention, a recovery tank for recovering the working fluid containing the powder overflowing or leaking from the working tank through the drain pipe is provided in the working fluid tank, and in the recovery tank. It is preferable to provide a pump and a collecting pipe for returning the working fluid containing the powder of (1) into the working tank.

[0009]

In the electric discharge machining method of the present invention, after the mirror finishing, the powder is directly recovered from the machining tank to the powder stocker, so that the powder does not settle in the machining fluid tank, the pipe and the cooler. The amount of mixture can be kept constant. Further, a processing liquid tank dedicated to powder mixing is unnecessary.

In the electric discharge machine of the present invention, since the powder stocker uses the filter cloth having the elastic member built therein, the pressure difference between the inside and the outside of the filter cloth after the collecting operation is eliminated, and the filter cloth is urged by the spring force. Expands and the powder adhering to the filter cloth is automatically released into the working fluid.

[0011]

1 is a block diagram showing an example of an apparatus for carrying out an electric discharge machining method according to the present invention. In the figure, 1 is a processing tank, 2
Is a working liquid tank, and the working liquid tank 2 is a waste liquid tank 2a.
And a cleaning liquid tank 2b. A work 4 and an electrode 5 whose positions are relatively controlled by a numerical controller are installed in the processing tank 1. Numeral 6 is a hopper for supplying or replenishing powder added to the processing tank 1 according to the present invention, and silicon powder, Al, TiC, W added to the processing liquid 7 during mirror finishing.
The powder 8 such as C, SiC, Si ₃ N ₄ or graphite powder is stored in the storage unit. The machining liquid 7 is pumped up from the cleaning liquid tank 2b for the purpose of this mirror finishing, or it is circulated and used during the electric discharge machining in the preceding steps such as rough machining, intermediate machining and semi-finishing machining. It is also possible to use the working fluid suitable for the condition as it is. Reference numeral 9 denotes a powder stocker additionally provided to the processing tank 1 according to the present invention. The powder stocker 9 is provided with a pipe 10 for sucking powder from the processing tank 1 together with the processing liquid 7 and a suction pump 11 and a valve 12. At the lower part of the powder stocker 9, a pipe 14 with a valve 13 for returning the powder to the processing tank 1 together with the processing liquid is connected,
A pipe 15 for returning the processing liquid to the processing tank 1 at the time of powder recovery is connected to the upper part of the powder stocker 9.

As shown in FIG. 2, the powder stocker 9 is in the form of a closed container, and a communication hole 17 is formed in the upper part of the inside thereof.
A partition wall 17 having a is provided, and a filter cloth 16 having a bag-shaped filter membrane is attached to the lower part of the partition wall 17 so as to surround the communication hole 17a, and a coil spring is provided inside the filter cloth 16. An elastic member 18 such as

Reference numeral 19 is a stirrer attached to the processing tank 1. The stirrer 19 is different from the conventional stirrer 20 shown in FIG. That is, the conventional agitator 20 is
The rotating flow a of the liquid 7 is generated around the impeller 20a, but the one used in the present embodiment, as shown in FIG. The liquid 7 is formed in the axial direction as a jet-shaped jet flow b, and a turbulent flow is generated in almost the entire area of the processing tank 1 by the agitator 19. As this agitator 19, FIG.
As shown in the side view of (C) and the bottom view of (D), a cylindrical strainer 19b is provided below the impeller 19a (this strainer 19b is arranged around the rotary shaft 19d integrally with the housing of the motor 19c). By providing a plurality of stays 19e), it is possible to restrict the flow of the jet jet flow, narrow the spread angle, and increase the jet flow velocity. According to subsequent experiments,
It was also effective to vibrate and agitate by vibrating an ultrasonic vibrator whose vibration energy was adjusted and set according to the size and capacity of the processing tank 1.

In FIG. 1, 21 is a pipe with a valve 22 for flowing the working liquid of the working tank 1 into the waste liquid tank 2a, and 23 is a pipe for purifying the liquid in the waste liquid tank 2a to the clean liquid tank 2b and sending it. A pump 24 and a filter 25 are installed in the pipe 23. Reference numeral 26 is a pipe with a pump 27 for supplying the liquid in the clean liquid tank 2b to the processing tank 1.

Using such a device, in rough machining and medium machining, as in the conventional case, the pump 27 sends the machining liquid from the clean liquid tank 2b into the machining tank 1 and the machining liquid cleaned by the filter 25, etc. In addition, the pipe 2 is made to overflow from the processing tank 1 and
1 is collected by flowing down into the sewage tank 2a via 1 and operating the pump 24 constantly or intermittently to purify the processing liquid from the sewage tank 2 by the filter 25 and send it to the cleaning liquid tank 2b, while Machining is performed by intermittently supplying a voltage pulse to the work 4 or discharging the electric charge stored in the capacitor.

In the case of mirror finishing, electrical processing conditions such as voltage pulse are switched, electrodes are exchanged if necessary, and oscillating motion is relatively given to machining feed in one axis direction as needed. And, as shown, processing tank 1
The valve 22b is provided below the hopper 6 while the valve 22 is closed, the pump 27 is stopped, the agitator 19 is operated, and the working fluid therein is at a predetermined level during normal processing.
Then, the powder 8 such as silicon is supplied into the processing tank 1 through the outlet pipe 6a to start the processing. In this case, the agitator 19
Turbulent flow is generated in almost the entire area of the processing tank 1 by the jet jet from the powder, and the powder is supplied to the processing gap between the electrode 5 and the workpiece 4 to perform the processing, and the powder is present in the processing gap. As a result, stable mirror surface processing is performed.

After the processing is completed, the valve 12 is opened, the agitator 19 is operated as necessary, and the pump 11 is operated to supply the processing liquid 7 containing the powder in the processing tank 1 to the pipe 1
0, the powder stocker 9, the pipe 15, and the processing tank 1 are circulated for 3 to 5 minutes, for example. During this circulating operation, a part of the processing waste (the processing waste is a small amount during the finishing process) and powder, preferably the majority of the mixed powder, are collected and attached to the filter cloth 16, so that the filter cloth 16 is filtered. The pressure difference between the inside and the outside of 16 occurs, and the elastic member 18 contracts due to the pressure difference, and the filter cloth 16 also contracts. However, when the pump 11 is stopped and the pressure difference disappears, the elastic member 18 expands or expands. Then, since the filter cloth 16 also expands or expands, the powder 8 collected and attached to the outer peripheral surface of the filter cloth 16 is desorbed and mixed in the working liquid in the stocker 9. After the powder is collected, the valve 22 is opened to collect the powder in the processing liquid waste liquid tank 2a of the processing tank 1, while the work 4 and the electrode 5 are detached and replaced.

At the time of the next mirror finishing, the liquid level in the processing tank 1 is adjusted and set so as not to overflow too much even if the powder and the processing liquid in the powder stocker 9 flow down.
3 is opened to allow the powder in the powder stocker 9 to flow into the processing tank 1 together with the processing liquid.

When the powder has reached the end of its life, the valve 22 is opened to allow the processing liquid containing the powder in the processing tank 1 to flow down into the waste liquid tank 2 and removed by the filter 25. Then, new powder 8 is supplied from the hopper 6 into the processing tank 1 for finishing.

In FIG. 1, the stocker 9 is a processing tank 1.
Although an example of being installed above the processing tank 1 is shown, when installing below the processing tank 1, as shown by the two-dot chain line in FIG.
The pipe 15 connected to the upper part of the powder stocker 9 is branched into a pipe 15A with a valve 28 for returning the processing liquid to the processing tank 1 and a pipe 15B with a valve 29 connected to the compressor 30, and the valve 28 is opened at the time of powder recovery. The valve 29 is closed when the valve 29 is closed to return the processing liquid to the processing tank 1 and the powder is returned to the processing tank 1.
8 is closed, valves 29 and 13 are opened, the working fluid in the stocker 9 is pressurized by compressed air, and the powder is piped together with the working fluid.
It is pushed up through 4 and returned to the processing tank 1. Further, instead of the compressor 30, it may be configured to be connected to the pipe 26.

FIG. 4 shows another embodiment of the present invention. As described above, when the powder-finished working liquid is used for the mirror finishing, the overflow weir 31 provided in the processing tank 1 overflows. The liquid 7a is stored in the liquid reservoir 32 so as to adjust the liquid surface, or is used mainly in an electric discharge machining apparatus or a vertically moving machining tank.
In an electric discharge machine equipped with a gutter 33 for receiving the leaked liquid,
The powder contained in the overflow or leakage liquid will be lost,
The working liquid containing the powder of the liquid reservoir 32 or the gutter 33 is caused to flow down through the drain pipes 34, 35 to the recovery tank 36 provided in the waste liquid tank 2a so as to project above the liquid surface. By returning the working liquid containing the powder accumulated in the processing tank 1 through the return pipe 37 to the processing tank 1 by the pump 38 provided in the pipe 37, loss of the powder is prevented. In this case, the liquid level detection operation by the upper and lower liquid level sensors 39 and 40 of the recovery tank 36 and the controller 41 to which the liquid level detection signal is input control the start and stop of the pump 38. The drain pipes 34 and 35 are omitted in FIG. 1, and the drain pipes 34 and 35 are connected to the pipe 2
1 and the pipe 21 is inserted into the recovery tank 36.

[0022]

According to the first aspect of the present invention, the powder is collected in the powder stocker and reused for the mirror finishing process, so that the occupied space is smaller than that of the working fluid tank dedicated to the powder mixing process. In addition, the powder can be reused, and the powder-mixed machining and the normal electric discharge machining can be switched efficiently and quickly.

According to the second aspect of the present invention, the jet jet generated by the stirrer causes turbulent flow, and the working fluid containing the powder is well agitated. Can be done.

According to the third aspect, the powder adhering to the filter cloth in the powder stocker is automatically desorbed into the working liquid at the end of the collecting operation, so that the powder collecting and reusing efficiency is improved.

According to the fourth aspect, since the powder contained in the overflowing or leaking working fluid is recovered, the waste of the powder is further reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an example of an apparatus for carrying out an electric discharge machining method according to the present invention.

FIG. 2 is a configuration diagram showing a powder stocker of the present embodiment.

3A is a schematic view of a conventional stirrer, FIG. 3B is a schematic view of the stirrer of the present embodiment, FIG. 3C is a side view of the stirrer of the embodiment, and FIG. It is a figure.

FIG. 4 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Processing Tank 2 Processing Liquid Tank 4 Work 5 Electrode 6 Hopper 7 Processing Liquid 8 Powder 9 Powder Stocker 16 Filter Cloth 17 Partition 18 Elastic Material 19 Stirrer 19b Strainer 25 Filter

Claims (4)

[Claims] 1. In a machining step other than final finishing, electric discharge machining is performed while circulating a machining fluid between a machining tank and a machining fluid tank, and powder is supplied in the machining step of the finishing machining. Alternatively, the powder is supplied into the processing tank from the hopper and the powder stocker to be replenished, the electric discharge machining is performed while stirring the powder with the processing liquid by the stirrer installed in the processing tank, and when the finishing process is finished, the powder stocker is processed. An electric discharge machining method characterized in that a machining fluid in a tank is pumped up and powder is collected. 2. The stirrer according to claim 1, wherein the stirrer is provided with a strainer if necessary and has an impeller for forming a jet-like jet flow, and the stirrer is used for almost the entire area of the processing tank. A method of electrical discharge machining, characterized in that a turbulent flow is generated in the workpiece, and the finish machining is performed in a state where the powder is supplied to the machining gap. 3. A powder storage hopper which is installed separately from the processing liquid tank and supplies or replenishes powder to the processing tank, and a powder stocker with a recovery pump which pumps up the processing liquid in the processing tank and recovers the powder. The powder stocker is installed in the processing tank and includes a stirrer for stirring and mixing the processing liquid and the powder in the processing tank. The powder stocker has a closed container shape, and a filter membrane through which the processing liquid is passed when the powder is collected. An elastic member is housed inside a filter cloth formed into a bag shape, and when the powder is collected, the working liquid is circulated from the outside to the inside of the filter cloth, and the elastic member is moved by the pressure difference between the inside and the outside of the filter cloth. An electric discharge machining apparatus having a structure in which the elastic member is contracted and the powder adhered to a filter cloth is detached when the flow of the machining fluid is stopped. 4. The processing tank according to claim 3, wherein a recovery tank for recovering the processing fluid containing the powder overflowing or leaking from the processing tank via a drain pipe is provided in the processing fluid tank, and the powder in the recovery tank is collected. An electric discharge machining apparatus comprising a pump and a recovery pipe for returning the machining fluid containing the same to the machining tank.