JPS6354490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of electric discharge machining and an electrode used to carry out the method.

In electrical discharge machining, an electrode and a workpiece are placed facing each other with a small gap in a machining liquid such as white kerosene, and a voltage is applied between them to generate an electric discharge.The discharge energy causes the workpiece to be moved to the electrode surface. However, as the machining progresses, fine sludge and carbon powder are generated in the gap between the electrode and the workpiece. Since these have a serious effect on processing stability and processing speed, how to remove them is a serious problem.

Conventionally, as a method for removing this sludge, etc., the electrode is made into a hollow body, a processing liquid reservoir is provided inside, and a processing liquid spout is provided on the bottom wall facing the workpiece, and the processing liquid is supplied from the outside to the processing liquid reservoir. A method has been adopted in which machining liquid is jetted from a spout into the gap between the electrode and the workpiece to carry away the generated sludge. With this method, sludge, etc. can be removed well, but on the other hand, if the flow rate of the machining fluid is too high, the surface roughness of the workpiece will deteriorate, so the flow rate of the machining fluid is controlled within a certain range. It is necessary to. However, since the gap between the electrode and the workpiece changes depending on the machining conditions, it is necessary to adjust the supply pressure of the machining fluid every time the machining conditions change, and it is difficult to control the flow rate of the machining fluid within a certain range. It was very difficult.

Furthermore, in addition to the above method, it has been conventionally practiced to move the electrode up and down to periodically widen the gap between the workpiece and the workpiece to promote the discharge of sludge, etc.
In this case, the gap between the electrode and the workpiece changes, making it more difficult to adjust the supply pressure of the machining fluid, and it is also difficult to adjust the negative and positive pressures generated in the machining fluid reservoir as the electrode moves up and down. It was also necessary to provide a hole in the electrode to suppress the pressure within a certain range, and to adjust the opening area of this hole depending on the generation of negative pressure and positive pressure.

The present invention solves the problems of the prior art as described above, creates a stable flow of machining fluid in the minute gap between the electrode and the workpiece, processes the workpiece at high machining speed, and achieves good results. The object of this invention is to provide an electric discharge machining method that can obtain surface roughness, and an electrode that can be suitably used to carry out the method.

The electric discharge machining method according to the present invention is characterized in that the liquid level of the machining fluid on one side of the microgap between the electrode and the workpiece is set higher than the liquid level on the other side by a predetermined amount. The objective is to perform electrical discharge machining while maintaining a stable flow of machining fluid in the minute gap using hydraulic pressure based on the difference in the fluid level.

Creating a stable liquid level difference on both sides of the minute gap between the electrode and the workpiece in this way is much easier than maintaining the liquid pressure supplied to the processing liquid reservoir constant as in the conventional method. Therefore, the flow of the machining fluid in the gap between the electrode and the workpiece is stabilized, sludge, etc. is removed well, and deterioration of the surface roughness of the workpiece surface due to excessive flow velocity of the machining fluid is prevented. It is.

In addition, the invention regarding the electrode is characterized by being hollow and having a processing liquid reservoir inside.
The bottom wall of the machining fluid tank is placed opposite the workpiece across a microgap to generate an electric discharge between the workpiece and the bottom wall, and the jetting fluid is spouted from the outside into the microgap. In an electrical discharge machining electrode that has an outlet, excess machining fluid overflows to a predetermined distance higher than the part of the electrode that is immersed under the fluid surface of the machining fluid tank, thereby lowering the fluid level of the machining fluid reservoir. The reason lies in the provision of an overflow port that maintains a constant height above the liquid level in the processing liquid tank.

If such an electrode is used, a larger amount of machining fluid can be supplied to the machining fluid reservoir than the amount of machining fluid spouted from the spout, and a certain amount of machining fluid can always overflow from the overflow port. By doing so, the hydraulic pressure of the machining fluid at the spout can be kept constant with high precision.
Sludge and the like are discharged well, stable electrical discharge occurs, and a good finished surface is obtained. By the way, if the electrode according to the present invention is used,
It has been confirmed through experiments that a machining speed approximately twice as high as that using conventional electrodes can be obtained.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In Fig. 1, 2 is the ram of the electric discharge machine.
It is moved up and down by a lifting mechanism (not shown) provided in the electrical discharge machine main body. A machining liquid tank 4 is provided below the ram 2, and a machining liquid such as white kerosene is supplied to the machining liquid tank 4 through a liquid supply pipe 6 by a pump (not shown). Processing liquid tank 4
A drain pipe 8 is connected to the bottom of the tank so that all of the machining fluid in the tank can be drained, and a drain port 10 is further provided at the top of the machining fluid tank 4.
When the drain pipe 8 is closed, the machining fluid flows out from the drain port 10, and the level of the machining fluid in the tank is maintained at the level of the drain port 10. In addition, in the figure, the drain port 10 is shown as being provided with a constant height, but in reality, the height of the drain port 10 can be changed arbitrarily, so that the machining fluid can be The surface can be set to a desired height.

A surface plate 12 is provided inside the machining liquid tank 4, and a mold 14 as a workpiece is fixed to this surface plate 12. On the other hand, an electrode 16 is fixed to the lower surface of the ram 2. This electrode 16 is connected to the upper plate 1
8. It is a hollow body having a side wall 20 and a bottom wall 22 and a processing liquid reservoir 24 inside, and is removably fixed to the ram 2 at the upper plate 18. The bottom wall 22 is connected to the workpiece surface 2 of the mold 14 as shown in FIG.
5 with a small gap 26 in between, and a machining fluid jet port 28 is formed in the bottom wall 22. A liquid supply port 3 is provided at an intermediate height position of the side wall 20.
0 is provided, and a liquid supply pipe line 32 is connected to this. Furthermore, an overflow port 3 is provided at the top of the side wall 20.
4 are provided. This overflow port 34 is used for natural overflow of the machining fluid supplied to the machining fluid reservoir 24 via the fluid supply pipe 32, excluding that which is spouted from the spout 28. The size is such that it can flow out without creating a pressure difference between the inside and outside of the mouth 34. Further, a sludge discharge port 36 is provided at the lowermost end of the side wall 20, that is, at a portion continuous to the bottom wall 22. The lower edge of the discharge port 36 is aligned with the upper surface of the bottom wall 22, so that sludge and carbon powder deposited on the bottom wall 22 can be easily removed. That is, it is unavoidable that the machining fluid supplied to the machining fluid reservoir 24 is mixed with a certain amount of sludge and carbon powder, and if there is no sludge discharge port 36, these sludge and carbon powder will flow to the bottom wall 22 of the machining fluid reservoir 24.
The sludge settles and accumulates in the sludge, which prevents stable discharge from occurring and reduces the machining speed. However, when the sludge discharge port 36 is provided, such problems do not occur. .

When performing electric discharge machining using the apparatus configured as described above, the mold 14 is fixed to the surface plate 12, the electrode 16 is fixed to the ram 2, and machining fluid is supplied from the liquid supply pipe 6. The machining fluid level in the machining fluid tank 4 is raised to the level of the fluid drain port 10. Thereafter, while the liquid supply from the liquid supply pipe line 6 is cut off, the supply of machining liquid to the electrode 16 through the liquid supply line 32 is started. The supplied machining fluid is ejected from the spout 28 into the gap 26, but since the amount of fluid supplied to the pipe line 32 is greater than this amount of ejected fluid, the liquid level in the machining fluid reservoir 24 rises and finally Excess machining fluid overflows from the overflow port 34. At this time, overflow port 34
is formed at a predetermined distance higher than the part of the electrode 16 that is submerged below the liquid surface of the machining liquid tank 4, so that the liquid level of the machining liquid reservoir 24 is more constant than the liquid level of the machining liquid tank 4. The amount will be kept high. Therefore, the fluid pressure difference before and after the gap 26 between the mold 14 and the electrode 16 is accurately maintained at an appropriate value, and the machining fluid flows through the gap 26 at an appropriate flow rate. As a result, sludge and carbon powder generated in the gap 26 are effectively removed, and the surface roughness of the processed surface 25 does not deteriorate due to an excessive flow rate of the processing fluid.

Moreover, the liquid level height of the machining liquid reservoir 24 and the liquid level of the machining liquid tank 4 are both kept constant by overflowing the excess machining liquid from the overflow port 34 and the liquid drain port 10, respectively. Therefore, as long as the amount of liquid supplied by the liquid supply pipe 32 is set to be larger than the maximum flow rate of the machining liquid spouted from the spout 28, the gap 26 will not fluctuate due to changes in machining conditions. Also, the difference in liquid level between the machining liquid reservoir 24 and the machining liquid tank 4 is kept accurately constant, and there is no need to adjust the flow rate of the liquid supply pipe 32. Furthermore, even when the electrode 16 is subjected to periodic vertical movements in order to improve the removal of sludge and the like from the gap 26, the liquid level in the machining liquid reservoir 24 can be easily kept constant; Since there is no generation of negative pressure and positive pressure that would occur when vertical movement is applied, there is no need to adjust the area of the opening to suppress these pressures within a certain range.

FIG. 3 shows another embodiment of the invention. In this embodiment, an overflow opening 34 is formed in the upper plate 18 of the electrode 16. Since the other parts are the same as those in the above embodiment, a detailed explanation will be omitted. However, according to this embodiment, the liquid level between the machining liquid reservoir 24 and the machining liquid tank 4 can be increased without increasing the length of the electrode 16. The difference can be increased.

In the above two embodiments, the ejection ports 28 are formed in the bottom wall 22 of the electrode 16 facing the workpiece, but these are not necessarily essential. For example, the method of the invention can also be carried out with an apparatus such as that shown in FIGS. 4 and 5. In the figure 4
0 is a processing liquid tank, 42 is a surface plate, 44 is a mold which is a workpiece, and 46 is an electrode. The mold 44 and the electrode 46 are surrounded by a container 48 . The two opposing side walls 50 of this container-like object 48 are provided very close to the side walls of the mold 44 and the electrode 46, while the other two side walls 52 and 54
is provided at a position sufficiently distant from the mold 44 and the electrode 46. Also, while sidewalls 50 and 52 are all the same height, sidewall 54 is lowered by a certain amount. The machining fluid is supplied from a fluid supply passage 56 formed in the electrode 46 to a machining fluid reservoir 58 surrounded by the mold 44, the electrode 46, and side walls 50 and 52, and the gap between the mold 44 and the electrode 46 is 60 and flows out to the machining fluid reservoir 62 on the opposite side. However, since the flow rate of the machining fluid supplied from the fluid supply passage 56 is greater than the flow rate of the machining fluid flowing through the gap 60, the machining fluid flows into the machining fluid reservoir 58 on the opposite side. On the side, an overflow port 6 formed at the upper end of the container-like object 48
Excess machining fluid will overflow from 4. On the other hand, the machining fluid flowing through the gap 60 and stored in the machining fluid reservoir 62 flows out over the upper end of the side wall 54 into the machining fluid tank 40 . The side wall 54 is connected to the other side wall 50 as described above.
and processing liquid reservoir 62 because it is lower than 52.
The liquid level is kept a certain amount lower than the liquid level in the machining liquid reservoir 58, and this liquid level difference accurately regulates the flow rate of the machining liquid flowing through the gap 60.
The same actions and effects as in the embodiment can be obtained.

Furthermore, in each of the above embodiments, the liquid level height of the machining liquid reservoirs 24, 58, etc. is fixed, but by making the height of the overflow port 34 adjustable, the liquid level can be adjusted. It is possible to adjust the height. Furthermore, instead of forming an overflow port directly on the electrode as shown in FIGS. 1 to 3, an overflow port is provided in a storage container provided separately from the electrode 16, and this container is connected to a sufficient flow path. It is also possible to maintain a constant liquid pressure in the space within the electrode by connecting it to the electrode with a flexible hose having a large area and adjusting the height of this reservoir. Furthermore, in the embodiment shown in FIGS. 4 and 5, the liquid supply passage 5
6 does not necessarily need to be provided on the electrode 46, and it is also possible to directly supply the machining fluid to the overflow port 64 of the machining fluid reservoir 58 from a separately provided fluid supply pipe.

In addition, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view schematically showing an apparatus according to an embodiment of the present invention, and FIG. 2 is a front sectional view showing an enlarged main part thereof. FIG. 3 is a diagram corresponding to FIG. 2 in another embodiment of the present invention. FIG. 4 is a front sectional view of a main part in yet another embodiment of the present invention, and FIG. 5 is a plan view of the same. 4, 40: Machining liquid tank, 14, 44: Mold (workpiece), 16, 46: Electrode, 20: Side wall, 22:
Bottom wall, 24, 58, 62: Processing liquid reservoir, 26, 6
0: Gap, 28: Spout port, 30: Liquid supply port, 34,
64: Overflow port, 36: Sludge discharge port, 4
8: Container-like object, 50, 52, 54: Side wall, 56:
Liquid supply passage.

Claims (1)

[Claims] 1. An electrode and a workpiece are opposed to each other with a small gap between them, and a machining liquid is flowed from one side of the small gap to the other side through the small gap. A method of machining the surface of the workpiece into a shape corresponding to the surface of the electrode by generating an electrical discharge between the workpiece and the workpiece, the method comprising: changing the level of the machining fluid on one side of the microgap to the other side; An electric discharge machining method characterized in that the liquid level is maintained at a predetermined amount higher than the liquid level on the side thereof, and a flow of the machining liquid is caused in the minute gap by hydraulic pressure based on the liquid level difference. 2. A hollow electrical discharge machining electrode having a machining liquid reservoir inside, which is placed opposite a workpiece with a minute gap in the machining liquid bath to generate an electric discharge between the workpiece and the workpiece. A portion of the electrode that is immersed below the liquid level of the machining liquid tank, in which the bottom wall has a spout for spouting machining liquid supplied from the outside into the minute gap. An electrode for electric discharge machining, characterized in that an overflow port is provided at a position higher than the machining fluid by a predetermined distance to cause surplus machining fluid to overflow and maintain the liquid level of the machining fluid reservoir at a constant height. 3. The electrical discharge machining electrode according to claim 2, wherein the external machining fluid supply port is provided at an intermediate height between the jet port and the overflow port. 4. The discharge according to claim 2 or 3, wherein a side wall continuous with the bottom wall and surrounding the machining liquid reservoir is provided with a sludge discharge port whose lower edge coincides with the upper surface of the bottom wall. Electrode for processing.