JPH04201119A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To obtain a high machining accuracy by providing an insulating layer between a subtank provided under a vertically-moving machining bath and a construction body such as a bed, etc., and moving a cooling liquid convectively to the insulating layer. CONSTITUTION:Even when the temperature of a dirty machining liquid in a subtank 8 is increased by machining, its heat is prevented from being conducted to a construction body such as a bed 5, etc., by a insulating layer 18 provided between the subtank 8 and the construction body such as the bed 5, etc., to eliminate adverse effect for precise machining. A cooling medium a is moved convectively to the inside of a flow path 18a and the insulating layer 18 by turning a fan 20. In this way, the internal surfaces of the subtank 8 are cooled by forced convection of the cooling medium a and the dirty machining liquid in the subtank 8 is also cooled. Thus, since the surfaces of the construction body such as the bed 5, etc., are also cooled at the same time and the insulating layer 18 is present, the construction body such as the bed 5. etc., will not be deformed, etc., by heat.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrical discharge machining device with high machining accuracy.

[Conventional technology]

FIG. 3 is a schematic side view showing an example of a conventional electric discharge machining apparatus. In the figure, (1) is the vertical direction of the figure (Z-axis direction)
(2) is a ram that moves in the horizontal direction (Y-axis direction) in the figure with the head (1), (3) is a ram (
2) is a saddle that moves in the front-rear direction (X-axis direction) in the figure, (4) is a column to which saddle (3) is attached, and (5)
) is bet. (6) is a table surface plate fixed on the bed (5), (7) is a processing tank lifting device (not shown)
(7a) is the processing tank (
7) is the machining fluid stored in the chamber.

A sub-tank (8) is provided at the lower part of the processing tank (7), and is attached closely to the structure of the bed (5) or is constructed integrally with the structure of the bed (5). (9
) is an electrode attached to the head (1) via a holder (10). Note that (11) is a workpiece attached to the table surface plate (6).

(12) is a machining fluid supply device that circulates machining fluid (7a) in the machining tank (7), (12a) is a machining fluid circulation pump, (
12b) is a filter device for removing processing waste generated by processing.

Although this example shows the case of one machining fluid circulation pump (12a), multiple units may be installed depending on the total amount of machining fluid (7a), the load condition, the capacity of the filter device (12b), etc. There is also. (13) is the bed (5) and processing tank (
7), the sealing part of the machining fluid (7a) interposed between the
14) is a discharge port for the machining fluid (7a), and (14a) is a drain valve. (15) is the machining fluid (7a) in the machining tank (7).
) A liquid level detection device such as a float switch (16) detects the amount of machining liquid in the sub tank (8).
This is an overflow port for discharging to. (17) is the sub tank (8) and the sewage tank (12) of the processing fluid supply device (12).
(described later) is a communication pipe that communicates between the two.

FIG. 4 shows details of the machining fluid supply device (12) shown in FIG. , (1
2d) and (12e) are a dirty liquid tank and a clean liquid tank separated by a partition plate (12).

(12f) is a first communication pipe that communicates the dirty liquid tank (12d) and the clean liquid tank (12e), (12h) is a filter pump that continues to operate when the power is turned on, and (121) is a filter. A filter device (12b) is configured. Note that (12g) is a second connecting pipe that communicates between the fresh liquid tank (12e) and the processing tank (7).

Next, the operation of the electric discharge machining apparatus configured as described above will be explained. First, the processing layer (7) is lowered by a processing tank lifting device (not shown), the workpiece (11) is attached to the table surface plate (6), and then the processing tank (7) is raised to an arbitrary position. let

Meanwhile, the electrode (9) is attached to the holder (10) and the ram (2
) and saddle (3) in the X and Y directions, and move the workpiece (
11) and then lower the head (1) to maintain the gap between the workpiece (11) and the electrode (9) at a predetermined value. In this state, the machining fluid supply device (12) is Processing liquid (7a) is supplied from the fresh liquid tank (12) into the processing tank (7). Then, the electrode (9) and the workpiece (1) are placed in this machining fluid.
1), a voltage is applied between the two and a submerged discharge is generated, and the workpiece (11) is machined into a desired shape.

A predetermined amount of machining fluid (7a) is supplied into the machining tank (7),
Also, the amount is maintained by a liquid level detection device (
15), and if the predetermined amount is not reached, the control device drives the machining fluid circulation pump (12a) based on the signal from the liquid level detection device (15) to replenish the machining fluid (7a), and also removes the excess machining fluid. The machining fluid is discharged from the machining tank (7) to the sub-tank (8) through the overflow port (16).

When machining is finished, the drain valve (14a) is opened to discharge the machining fluid in the machining tank (7) to the sub-tank (8). The discharged processing liquid is led to the waste liquid tank (12d) of the processing liquid supply device (12) through the communication pipe (17).

In this way, the processed sewage stored in the sewage tank (12d) is transferred to the filter device (12b) as shown in FIG.
The liquid is pressurized by the filter pump (12h), passes through the filter (12i), and is stored in the fresh liquid tank (12e) in a clean state where processing waste is removed. When starting a new machining process or replenishing the machining fluid (7a) during machining work, the machining fluid circulation pump (12a) supplies the cleaned machining fluid (7a) to the machining tank (7). In this way, the machining fluid circulates throughout the system.

The operating state of the machining fluid circulation pump (12a) is controlled by a control device (not shown), or the filter pump (12h) continues to operate with the power turned on. Therefore, the supply of machining liquid from the dirty liquid tank (12d) to the clean liquid tank (12e) may become excessive, and in this case,
Excess machining fluid (7a) in the cleaning fluid (12e) overflows from the top of the partition plate (12C) to the dirty fluid tank (12d), and the machining fluid circulates inside the machining fluid supply device (12).

[Problems to be Solved by the Invention] The sub-tank (8) of the conventional electrical discharge machining apparatus configured as described above is installed in close contact with the bed (5) or as a part of the structure. Therefore, the heat of the machining fluid in the sub-tank (8) is easily conducted directly to the bed (5), etc.
There is a problem in that the structure such as the bed (5) is thermally deformed and the relative positional relationship between the electrode (9) and the workpiece (11) changes, resulting in a decrease in machining accuracy.

That is, in electric discharge machining, the electrode (9) and the workpiece (11
) to perform machining by generating a submerged discharge between the
The temperature of the machining fluid (7a) interposed between the two rises.

This is because when the flowing current is increased to increase the machining speed, the machining fluid (7a) whose temperature has risen significantly due to X0 electrical discharge machining is discharged into the sub-tank (8) through the overflow port (16). However, the heat is transferred to structures such as the bed (5), causing the above-mentioned problems.

Furthermore, a machining fluid supply device (12
), the sub-tank (
8) The temperature of the machining fluid inside may rise and the machining accuracy may decrease. That is, if the machining fluid circulation pump (12a) is stopped while the filter pump (12h) is continuously operating, and the machining fluid continues to circulate inside the machining fluid supply device (12), the filter pump (12h) ) is accumulated inside the machining fluid supply device (12). The heat accumulated in the pollution tank (12d) in this way is
This is because the machining fluid in the communication pipe (17) is transferred to the sub-tank (8) by heat conduction and natural retention.

The present invention has been made to solve the above-mentioned problems, and by preventing the heat of the machining fluid in the sub-tank from being conducted to structures such as beds, the present invention prevents heat deformation of structures such as beds. The purpose of this invention is to eliminate changes in the relative positional relationship between an electrode and a workpiece and to obtain an electric discharge machining device with high machining accuracy.

[Means for Solving the Problems] The electrical discharge machining apparatus according to the present invention is one in which a heat insulating layer is provided between a sub-tank provided at the bottom of a machining tank that moves in the vertical direction and a structure such as a bed. be.

Further, the cooling medium is caused to flow through the heat insulating layer.

[Effect] When a workpiece is subjected to electrical discharge machining, the temperature of the machining fluid increases.

This heat is prevented from being conducted by a heat insulating layer provided between the sub-tank at the bottom of the processing tank and the structure such as the bed, and is not transmitted to the structure such as the bed.

In addition, by convection of the cooling medium through the heat insulating layer,
More efficiently prevents heat conduction to the structure.

Embodiment of the Invention FIG. 1 is a schematic side view showing an embodiment of the invention. Note that the same or equivalent parts as in the conventional example shown in FIGS. 3 and 4 are given the same reference numerals, and the explanation thereof will be omitted.

(18) is a heat insulating layer consisting of a space formed between a sub-tank (8) provided at the bottom of the processing tank (7) that moves in the vertical direction and a structure such as a bed (5). holds air (thermal conductivity k -0,024 W/m-K). (19) is a spacer for holding the heat insulating layer (18) and fixing the sub-tank (8) to a structure such as the bed (5). For this spacer (19), it is best to use a material with as low a thermal conductivity as possible, such as steel (thermal conductivity -50 W/m-K), and to minimize the contact area as much as possible, since it can be omitted. If so, it is better not to provide it.

Note that while the amount of heat transferred by radiation is proportional to the fourth power of the temperature difference, normally the temperature rise of the processing sewage in the sub-tank (8) is not so large, so heat transfer by radiation does not pose a problem. .

Next, the operation of the present invention constructed as described above will be explained with reference to FIGS. 1 and 4. Note that the setup and processing operations before processing are the same as conventional ones.

In this embodiment, even if the temperature of the processed wastewater in the subtank (8) rises due to processing, the heat is transferred to the subtank (8).
The heat insulating layer (18) provided between the structure (8) and the bed (5) prevents conduction to the structure such as the bed (5), and precision machining is not adversely affected.

Furthermore, even if the temperature rise of the processed sewage caused by the continuous operation of the filter pump (12 hours) is transmitted to the processed sewage in the sub-tank (8) via the communication pipe (17), the same applies as in the above case. Heat conduction to the structure is then prevented by the thermal insulation layer (18).

FIG. 2 is a schematic side view showing another embodiment of the present invention.

(18) is a heat insulating layer provided between the sub-tank (8) and a structure such as the bed (5). (18a) is a flow path provided in a structure such as a bed (5) and communicating with a heat insulating layer (18), and a cooling medium a such as air is inside the heat insulating layer (18) and the flow path (18a). Convection flows in the direction of the arrow. (19) is a spacer for holding the heat insulating layer (18) and fixing the sub-tank (8) to a structure such as the bed (5), and is made of a material that allows air to circulate or is provided with air circulation holes. It is being

(20) connects the cooling medium a to the flow path (18a) and the heat insulating layer (18).
) is a fan to force convection within the air.

In this embodiment configured as described above, the fan (2
0) to cause convection of the cooling medium a within the flow path (18a) and the heat insulating layer (18). In this way, the surface inside the sub-tank (8) is cooled by the forced convection of the cooling medium a, and the processing sewage inside the sub-tank (8) is also cooled. Therefore, the surface of the structure such as the bed (5) is also cooled at the same time, and together with the presence of the heat insulating layer (18), the bed (5)
5) No thermal deformation or the like occurs in the structure.

In the embodiment shown in Fig. 1, air is present inside the heat insulating layer (18) consisting of a space, but this space may be filled with a so-called heat insulating material such as glass wool, asbestos, or styrofoam. However, natural convection heat transfer of gas may be prevented to improve heat insulation.

In addition, although we have shown the case where the spacer (19) is made of steel, it is generally made of ceramic (19), which has a lower thermal conductivity.
Thermal conductivity k -I W / m-), so-called synthetic resins such as epoxy and polycarbonate (thermal conductivity k
= 0.3 W/m-K) is more effective. However, when deciding on materials and shapes,
It is necessary to consider not only heat insulation properties but also workability, assemblability, strength, etc.

Furthermore, although FIG. 2 shows the case where the cooling medium a is caused to flow into the structure by the fan (20), the cooling medium a may be sucked out conversely. Further, although air at room temperature is used as the cooling medium a, the temperature of the cooling medium flowing in may be controlled to a desired temperature by a temperature control device. In addition, since the machining fluid supplied from the machining fluid supply device to the machine body is usually temperature-controlled, a portion of it may be used as a cooling medium (or a dedicated temperature control circuit may be configured and Freon, etc. Cooling can also be performed using a refrigerant.Furthermore, fins or the like can be installed on the surface of the structure such as the sub-tank (8) or the bed (5) in which the heat insulating layer (18) is interposed to improve heat conduction by forced convection. May be promoted.

[Effects of the Invention] As is clear from the above description, the present invention provides a heat insulating layer between a sub-tank provided at the bottom of a vertically moving processing tank and a structure such as a bed, or Since the cooling medium is convected in the layer, the heat of the machining fluid in the sub-tank is not conducted to structures such as the bed, and the relative position of the electrode and workpiece due to thermal deformation of structures such as the bed is prevented. Changes in the relationship can be prevented and electrical discharge machining devices with different machining accuracy can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an embodiment of the present invention, FIG. 2 is a schematic side view showing another embodiment of the present invention, and FIG. 3 is a schematic side view showing an example of a conventional electric discharge machining apparatus. FIG. 4 is a schematic side view showing an enlarged main part of FIG. 3. In the figure, (5) is a bed, (7) is a processing tank, (8) is a sub-tank, (18) is a heat insulating layer, and a is a cooling medium. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) In electrical discharge machining equipment in which a machining tank that stores machining fluid moves in the vertical direction, a heat insulating layer is provided between a sub-tank provided at the bottom of the machining tank and a structure such as a bed. Characteristic electrical discharge machining equipment. (2) The electrical discharge machining apparatus according to claim (1), characterized in that a cooling medium is caused to flow through the heat insulating layer.