Wire electric discharge machining device

Abstract

This wire electric discharge machine (100) comprises a processing tank (6), a wire electrode (7), a lower arm (8), a lower wire guide (10), and a bellows member (11). An opening (60) through which the lower arm (8) passes is formed in the processing tank (6). The bellows member (11) is disposed so that, among both cylindrical ends, the opening provided at one end is sealed and the other end surrounds the periphery of the opening (60) of the processing tank (6), and the space between the inside of the cylinder of the bellows member (11) and the inside of the processing tank (6), in which a processing liquid is stored, is sealed so that the processing liquid does not leak out from the inside of the processing tank (6) even if the relative position between the lower wire guide (10) and the processing tank (6) changes.

Description

Wire Electrical Discharge Machine

[0001] The present disclosure relates to a wire electrical discharge machine.

[0002] Conventionally, wire electric discharge machines are known that machine a workpiece by generating a voltage between the workpiece and a wire electrode to generate an electric discharge. For example, Patent Document 1 discloses an electric discharge machining apparatus including a machining tank for storing a machining fluid, a lower guide arm extending from the inside to the outside of the machining tank, and a cylindrical bellows-shaped seal member surrounding the lower guide arm outside the machining tank. The machining tank has an elongated opening through which the lower guide arm passes. Flanges are provided at both ends of the bellows-shaped seal member along the opening edges at both ends. The flange portion provided at one end of the bellows-shaped seal member is attached along the opening edge of the elongated opening from the outside of the machining tank to close the elongated opening and seal between the bellows-shaped seal member and the elongated opening. The flange portion provided at the other end of the bellows-shaped seal member is attached to a column provided on the upper surface of a base to seal between the bellows-shaped seal member and the column.

[0003] Japanese Unexamined Patent Publication No. 7-1241

[0004] However, in the technology described in Patent Document 1, the interior of the machining tank and the interior of the bellows-shaped seal are connected, so the interior of the bellows-shaped seal is filled with machining fluid. That is, the lower guide arm disposed inside the bellows-shaped seal is immersed in the machining fluid. Therefore, when the temperature of the machining fluid rises during machining of the workpiece, the lower guide arm holding the wire electrode thermally expands, potentially causing the wire electrode to shift from its target position and degrading the machining accuracy of the workpiece. Furthermore, workpiece debris that enters the bellows-shaped seal along with the machining fluid accumulates in the grooves on the inner surface of the bellows over time. This debris exerts a load on the bellows-shaped seal due to its expansion and contraction, potentially degrading the machining accuracy of the workpiece.

[0005] The present disclosure has been made in view of the above, and has an object to provide a wire electric discharge machine that can suppress deterioration in machining accuracy of a workpiece.

[0006] To solve the above-mentioned problems and achieve the object, the present disclosure provides a wire electric discharge machine including a machining tank for storing machining fluid, a wire electrode for electrical discharge machining of a workpiece immersed in the machining fluid by generating an electric discharge between the wire electrode and the workpiece, a lower arm extending from the inside to the outside of the machining tank, a lower wire guide attached to the lower arm and positioned inside the machining tank for holding the wire electrode, and a cylindrical bellows member positioned inside the machining tank and surrounding the lower arm located inside the machining tank. The machining tank has an opening through which the lower arm passes. The bellows member has an opening at one end of the cylindrical shape that is closed, and the other end that is positioned to surround the opening of the machining tank, thereby sealing the space between the cylindrical interior of the bellows member and the interior of the machining tank in which the machining fluid is stored to prevent leakage of the machining fluid from inside the machining tank even if the relative position of the lower wire guide and the machining tank changes.

[0007] The wire electric discharge machine according to the present disclosure has the effect of suppressing deterioration in the machining accuracy of the workpiece.

[0008] 5A and 5B are cross-sectional views taken along the line V-V in FIG. 2; 14 is an explanatory diagram showing a state in which the machining tank has been moved in the Y-axis direction in a wire electric discharge machine; FIG. 15 is a perspective view showing a modified example of the wire electric discharge machine according to the embodiment; FIG. 16 is an explanatory diagram showing an example of a wire electric discharge machine according to a comparative example; FIG. 17 is an explanatory diagram showing an example of a lower arm and a bellows member in a wire electric discharge machine according to a comparative example;

[0009] Hereinafter, a wire electric discharge machine according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] 1 is a perspective view of a wire electric discharge machine according to an embodiment. FIG. 2 is a front view of a wire electric discharge machine according to an embodiment. FIG. 3 is a side view of a wire electric discharge machine according to an embodiment. FIG. 4 is an enlarged view of a main part of a wire electric discharge machine according to an embodiment. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 2. FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5, schematically showing a main part. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 6. In FIGS. 1 to 5, the machining tank 6 is shown with a dashed line to clearly show other components.

[0011] 1 , a wire electric discharge machine 100 according to this embodiment machines a workpiece W by immersing the workpiece W inside a machining tank 6 that stores machining fluid and generating a voltage between the workpiece W and a wire electrode 7 to cause discharge. The wire electric discharge machine 100 according to this embodiment includes a bed 1, a column 2, a Y-axis table 3, an X-axis table 4, a Z-axis base 5, the machining tank 6, the wire electrode 7, a lower arm 8, an upper wire guide 9, a lower wire guide 10, and a bellows member 11.

[0012] As shown in Figures 1 to 3, bed 1 is the base of wire electric discharge machine 100. A column 2 is installed on the rear side of the upper surface of bed 1, and a Y-axis table 3 is installed on the front side. The column 2 has its lower end fixed to bed 1 and is installed so as to extend upward from the upper surface of bed 1. A Z-axis base 5 is installed on the upper part of column 2, extending horizontally from column 2 toward the front. A lower arm 8 is installed on the lower part of column 2, extending horizontally from column 2 toward the front.

[0013] As shown in Figures 1 to 3, the Y-axis table 3 moves in the Y-axis direction, which is the direction from the back to the front of the bed 1. The Y-axis table 3 itself moves, thereby moving the X-axis table 4 and the machining tank 6 in the Y-axis direction. The X-axis table 4 is installed on the upper surface of the Y-axis table 3. The X-axis table 4 moves horizontally in the X-axis direction, which is perpendicular to the Y-axis direction. The X-axis table 4 itself moves, thereby moving the machining tank 6 in the X-axis direction. The Y-axis table 3 and the X-axis table 4 may be arranged in reverse. That is, the X-axis table 4 may be arranged on the upper surface of the bed 1, and the Y-axis table 3 may be arranged on the upper surface of the X-axis table 4. The Z-axis base 5 is installed on top of the column 2 so as to protrude from the column 2 toward the front. The machining tank 6 is located below the Z-axis base 5. The Z-axis base 5 is configured to be movable in the Z-axis direction (up and down) along the column 2 by a movement mechanism (not shown). An upper wire guide 9 is attached to the tip of the Z-axis base 5. The driving of the Y-axis table 3, the X-axis table 4, and the Z-axis base 5 is controlled simultaneously or separately by a controller (not shown). Note that the horizontal direction mentioned above does not need to be strictly horizontal, but may be approximately horizontal.

[0014] As shown in Figures 1 to 3, the machining tank 6 is installed on the upper surface of the X-axis table 4. The machining tank 6 can be moved in the Y-axis and X-axis directions by the Y-axis table 3 and the X-axis table 4. A machining fluid is stored inside the machining tank 6. The workpiece W is fixed inside the machining tank 6 and immersed in the machining fluid. By immersing the workpiece W in the machining fluid, deterioration of machining accuracy due to thermal expansion and thermal contraction of the workpiece W can be suppressed. As shown in Figure 6, an opening 60 through which the lower arm 8 passes is formed on the back surface of the machining tank 6 facing the column 2.

[0015] 4, the wire electrode 7 generates an electric discharge between itself and the workpiece W immersed in the machining fluid in the machining tank 6, thereby performing electric discharge machining on the workpiece W. The upper end of the wire electrode 7 is held by an upper wire guide 9. The lower end of the wire electrode 7 is held by a lower wire guide 10. The wire electrode 7 is fed by a wire feeding mechanism (not shown) and wound up by a wire winding mechanism (not shown).

[0016] As shown in Figures 3 to 5, the lower arm 8 is provided at the bottom of the column 2 so as to protrude from the column 2 toward the front. The lower arm 8 extends from the inside to the outside of the machining tank 6 through an opening 60. As shown in Figure 7, the lower arm 8 has a rectangular vertical cross section and a flat upper surface. A lower wire guide 10 is attached to the tip of the lower arm 8. The rear end of the lower arm 8 is fixed to the column 2 with a fixing member such as a bolt.

[0017] 1 to 3, the upper wire guide 9 is attached to the tip of the Z-axis base 5 and holds the upper end of the wire electrode 7 above the workpiece W. The upper wire guide 9 moves in the Z-axis direction together with the Z-axis base 5 as the Z-axis base 5 moves.

[0018] 3 and 4 , the lower wire guide 10 is attached to the tip of the lower arm 8 and is disposed inside the machining tank 6. The lower wire guide 10 holds the lower end of the wire electrode 7 below the workpiece W. The wire electric discharge machine 100 uses the wire electrode 7 positioned by the upper wire guide 9 and the lower wire guide 10 to machine the workpiece W into a desired shape.

[0019] FIG. 8 is a cross-sectional view of the main components of the lower wire guide 10 taken along the line VIII-VIII in FIG. 5 . FIG. 9 is a perspective view of the main components shown in FIG. 8 . As shown in FIGS. 8 and 9 , the lower wire guide 10 includes a holding portion 10a, an insulating member 10b, and an intermediate member 10c. The holding portion 10a holds the lower end of the wire electrode 7. The insulating member 10b is a flat plate-shaped member. The insulating member 10b is made of, for example, a ceramic material such as alumina or glass-reinforced epoxy resin. One side of the insulating member 10b is attached to the holding portion 10a, and the other side opposite the one side is attached to the distal end surface of the lower arm 8, providing insulation between the holding portion 10a and the lower arm 8. The intermediate member 10c is, for example, a square steel pipe. The intermediate member 10c is attached to the insulating member 10b, and the lower arm 8 passes through it. Flanges 10d and 10e are formed at both ends of the intermediate member 10c along the opening edges. One flange portion 10d of the intermediate member 10c is fixed to the insulating member 10b with a fixing member 13 such as a screw. A sealing member 17 such as a packing is provided between the flange portion 10d and the insulating member 10b. An opening of one end of the intermediate member 10c fixed to the insulating member 10b is closed by the insulating member 10b. The lower wire guide 10 is attached to the tip portion of the lower arm 8 by fixing the insulating member 10b with a fixing member 14 such as a screw to the tip surface of the lower arm 8, which is inserted into the cylindrical intermediate member 10c.

[0020] As shown in Fig. 7, the bellows member 11 has a rectangular cylindrical shape. As shown in Figs. 6 to 9, the bellows member 11 is disposed inside the machining tank 6 and surrounds the periphery of the lower arm 8 located inside the machining tank 6. The bellows member 11 is disposed so that an opening at one end of the cylindrical shape is closed and the other end surrounds the periphery of the opening 60 of the machining tank 6, thereby sealing the space between the cylindrical interior of the bellows member 11 and the interior of the machining tank 6 in which the machining fluid is stored.

[0021] 8 and 9, the bellows member 11 has a cylindrical main body 11a with a bellows structure, a first connecting portion 11b provided at one end of the main body 11a, and a second connecting portion 11c provided at the other end of the main body 11a. The main body 11a is made of, for example, synthetic rubber or synthetic resin. The main body 11a has a rectangular cylindrical shape and has a flat surface that faces the flat upper surface of the lower arm 8. The main body 11a surrounds the lower arm 8 located inside the processing tank 6.

[0022] The first connecting portion 11b is, for example, a flange provided along the opening edge of the main body portion 11a. The first connecting portion 11b is, for example, a metal fitting. The first connecting portion 11b is connected to the other flange portion 10e of the intermediate member 10c with a fixing member 15 such as a screw. A sealing member 18 such as a packing is provided between the first connecting portion 11b and the flange portion 10e of the intermediate member 10c. The second connecting portion 11c is, for example, a flange provided along the opening edge of the main body portion 11a. The second connecting portion 11c is, for example, a metal fitting. The second connecting portion 11c abuts along the periphery of the opening 60 from the inside of the processing tank 6 and is connected to the inner surface of the processing tank 6 with a fixing member 16 such as a screw. A sealing member 19 such as a packing is provided between the second connecting portion 11c and the inner surface of the processing tank 6. That is, the bellows member 11 is attached to the machining tank 6 with the first connecting portion 11b attached to the lower wire guide 10, the opening provided at one end blocked by the insulating member 10b, and the second connecting portion 11c disposed so as to surround the periphery of the opening 60 of the machining tank 6. As a result, even if the relative position of the lower wire guide 10 and the machining tank 6 changes on the plane in which the machining tank 6 can move, the bellows member 11 seals the space between the inside of the cylinder of the bellows member 11 and the interior of the machining tank 6 in which the machining fluid is stored, so that the machining fluid in the machining tank 6 does not leak into the cylinder of the bellows member 11 over the entire range of that change.

[0023] The first connecting portion 11b and the second connecting portion 11c are not limited to the flanges shown in the drawings and may have other shapes. Furthermore, the first connecting portion 11b is not limited to being attached to the insulating member 10b of the lower wire guide 10 via the intermediate member 10c and may be attached directly to the insulating member 10b of the lower wire guide 10, for example. In short, the first connecting portion 11b and the second connecting portion 11c may have any configuration as long as they can seal the space between the cylindrical interior of the bellows member 11 and the interior of the processing tank 6.

[0024] FIG. 10 is an explanatory diagram showing the wire electric discharge machine according to the embodiment in a state where the machining tank is moved in the X-axis direction. FIG. 11 is an explanatory diagram showing the wire electric discharge machine according to the embodiment in a state where the machining tank is moved in the Y-axis direction. Note that the outline arrows in FIGS. 10 and 11 indicate the movement direction of the machining tank 6. In addition, in FIGS. 10 and 11, the machining tank 6 is shown with a dashed line to clearly show other components. As shown in FIG. 10, the bellows member 11 expands and contracts in the X-axis direction by movement of the X-axis table 4. As shown in FIG. 11, the bellows member 11 expands and contracts in the Y-axis direction by movement of the Y-axis table 3. That is, the bellows member 11 expands and contracts in two axial directions, the X-axis direction and the Y-axis direction.

[0025] Fig. 12 is a perspective view showing a modified example of the wire electric discharge machine according to the embodiment. As shown in Fig. 12, the bellows member 11 may be trapezoidal in plan view so that the internal space expands from one end attached to the lower wire guide 10 toward the other end attached to the inner surface of the machining tank 6. Furthermore, the bellows member 11 is not limited to the rectangular shape in plan view shown in Fig. 5 or the trapezoid shape shown in Fig. 12, and may have any other shape, such as an oval cross section, as long as it is expandable and contractible in two axial directions, that is, the X-axis and the Y-axis.

[0026] Fig. 13 is an explanatory diagram schematically illustrating an example of a wire electric discharge machine of a comparative example. As shown in Fig. 13, in the wire electric discharge machine 100A of the comparative example, a cylindrical bellows member 12 is arranged outside the machining tank 6. The machining tank 6 has an opening 60 through which the lower arm 8 passes. One end of the bellows member 12 is arranged along the edge of the opening 60 and is attached to the outer surface of the machining tank 6 with a fixing member such as a screw, thereby closing the gap with the opening 60. The other end of the bellows member 12 is attached to the side surface of the column 2 with a fixing member such as a screw.

[0027] In the comparative example of wire electric discharge machine 100A shown in Figure 13, the interior of the machining tank 6 and the interior of the bellows member 12 are connected, so the interior of the bellows member 12 is filled with machining fluid. That is, the lower arm 8 disposed inside the bellows member 12 is immersed in the machining fluid. Therefore, when the temperature of the machining fluid rises due to machining of the workpiece W, the lower arm 8 thermally expands, which may cause the wire electrode to shift from the target position and degrade the machining accuracy of the workpiece W. Furthermore, machining debris that has entered the interior of the bellows member 12 along with the machining fluid accumulates over time in the grooves on the inner surface of the bellows member 12, and this machining debris acts as a load on the expansion and contraction of the bellows member 12, which may degrade the machining accuracy of the workpiece W.

[0028] On the other hand, a wire electric discharge machine 100 according to this embodiment includes a machining tank 6 in which machining fluid is stored, a wire electrode 7 that generates an electric discharge between the wire electrode 7 and a workpiece W immersed in the machining fluid in the machining tank 6 to perform electric discharge machining on the workpiece W, a lower arm 8 that extends from the inside to the outside of the machining tank 6, a lower wire guide 10 that is attached to the lower arm 8 and disposed inside the machining tank 6 to hold the wire electrode 7, and a cylindrical bellows member 11 that is disposed inside the machining tank 6 and surrounds the periphery of the lower arm 8 located inside the machining tank 6. The bellows member 11 has an opening 60 through which the lower arm 8 passes. The bellows member 11 has an opening at one end of its cylindrical shape that is closed, and the other end that is disposed so as to surround the periphery of the opening 60 of the machining tank 6, and seals the space between the cylindrical interior of the bellows member 11 and the interior of the machining tank 6 in which the machining fluid is stored so as to prevent leakage of the machining fluid from inside the machining tank 6 even if the relative positions of the lower wire guide 10 and the machining tank 6 change. That is, since the lower arm 8 is surrounded by the bellows member 11 , it is not immersed in the machining fluid and is not affected by the temperature of the machining fluid in the machining tank 6 .

[0029] Therefore, the wire electric discharge machine 100 according to this embodiment can suppress thermal expansion of the lower arm 8, thereby suppressing deterioration in the machining accuracy of the workpiece W. Furthermore, because machining debris does not accumulate in the grooves on the inner surface of the bellows member 11, the accumulation of machining debris in the grooves can be prevented, preventing the expansion and contraction of the bellows member 11 and preventing a decrease in the positional accuracy of the wire electrode 7 relative to the workpiece W. Therefore, the wire electric discharge machine 100 can suppress deterioration in the machining accuracy of the workpiece W due to the machining debris. It is conceivable that machining debris may accumulate in the grooves on the outer surface of the bellows member 11. However, inside the machining tank 6, the machining fluid flows due to repeated inflow and outflow. That is, even if machining debris generated by wire electric discharge machining reaches the outer surface of the bellows member 11, it is swept away by the flow of machining fluid and does not become a burden on the expansion and contraction of the bellows member 11.

[0030] FIG. 14 is an explanatory diagram schematically illustrating an example of a lower arm and a bellows member in a wire electric discharge machine of a comparative example. FIG. 15 is an explanatory diagram schematically illustrating a state in which the bellows member 11 is extended or contracted along the X-axis direction from the state shown in FIG. 14 in a wire electric discharge machine of a comparative example. Because the bellows member 11 is disposed inside the machining tank 6 filled with machining fluid, there is a risk that it will sag downward due to its own weight and the hydraulic pressure of the machining fluid. If the bellows member 11 sags and becomes deformed, it may not be able to extend or contract in response to the movement of the machining tank 6. Therefore, the bellows member 11 is held on the upper surface of the lower arm 8 to prevent it from sagging. However, for example, as shown in FIG. 14 , if the longitudinal cross section of the lower arm 8A is circular, the contact area between the outer surface of the lower arm 8A and the inner surface of the bellows member 11 is small, and the area in which the bellows member 11 is held by the lower arm 8A is small. 15 , when the bellows member 11 expands and contracts along the X-axis direction and the lower arm 8A reaches one of the inner surfaces of the bellows member 11, the distance between the contact point between the lower arm 8A and the bellows member 11 and the other inner surface of the bellows member 11 increases. In this case, the bellows member 11 is subjected to a large load on the other side surface due to its own weight and the hydraulic pressure of the machining fluid, causing it to sag downward.

[0031] 7, the lower arm 8 in this embodiment has a rectangular cross section and a flat upper surface. The bellows member 11 has a rectangular cylindrical shape and a flat surface that faces the flat upper surface of the lower arm 8. This allows for surface contact between the upper surface of the lower arm 8 and the flat surface of the bellows member 11, increasing the area over which the lower arm 8 holds the bellows member 11.

[0032] Figure 16 is an explanatory diagram schematically illustrating a state in which the bellows member 11 in the wire electric discharge machine according to the embodiment has expanded or contracted along the X-axis direction from the state shown in Figure 7. As shown in Figure 16, even when the bellows member 11 expands or contracts along the X-axis direction and the lower arm 8 reaches one inner surface of the bellows member 11, the distance from the position where the lower arm 8 and the bellows member 11 make surface contact to the other inner surface of the bellows member 11 can be small. In other words, the wire electric discharge machine 100 according to the present embodiment can prevent the bellows member 11 from sagging due to its own weight and the hydraulic pressure of the machining fluid.

[0033] The vertical cross-sectional shape of the lower arm 8 is not limited to a rectangular shape. The lower arm 8 may have another shape as long as it has a flat upper surface. The bellows member 11 is not limited to a rectangular cylindrical shape. The bellows member 11 may have another shape as long as it has a flat surface that faces the flat upper surface of the lower arm 8.

[0034] In addition, in the present embodiment, the Y-axis table 3 and the X-axis table 4 are used to move the machining tank 6 in the X-axis and Y-axis directions to machine the workpiece W, but this configuration is not limiting. For example, the Y-axis table 3 and the X-axis table 4 may be installed at the lower end of the column 2. In this case, the column 2 moves in the X-axis and Y-axis directions, thereby moving the wire electrode 7 in the X-axis and Y-axis directions, and machining the workpiece W. Furthermore, one of the Y-axis table 3 and the X-axis table 4 may be installed below the machining tank 6, and the other may be installed below the column 2.

[0035] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention.

[0036] REFERENCE SIGNS LIST 1 bed, 2 column, 3 Y-axis table, 4 X-axis table, 5 Z-axis base, 6 machining tank, 7 wire electrode, 8, 8A lower arm, 9 upper wire guide, 10 lower wire guide, 10a holding portion, 10b insulating member, 10c intermediate member, 10d, 10e flange portion, 11, 12 bellows member, 11a main body portion, 11b first connection portion, 11c second connection portion, 13, 14, 15, 16 fixing member, 17, 18, 19 sealing member, 60 opening, 100, 100A wire electric discharge machine, W workpiece.

Claims

1. A wire electrical discharge machining apparatus comprising: a machining tank for storing a machining fluid; a wire electrode for discharging between the machining tank and a workpiece immersed in the machining fluid in the machining tank to perform electrical discharge machining on the workpiece; a lower arm extending from inside to outside of the machining tank; a lower wire guide attached to the lower arm and disposed inside the machining tank for holding the wire electrode; and a cylindrical rubber member disposed inside the machining tank and surrounding the periphery of the lower arm located inside the machining tank. The machining tank is formed with an opening through which the lower arm passes. One end of the cylindrical rubber member is provided with a closed opening, and the other end is disposed so as to surround the periphery of the opening of the machining tank, and the inside of the cylinder of the rubber member closes the space between the inside of the machining tank where the machining fluid is stored to prevent the machining fluid from leaking even when the relative position between the lower wire guide and the machining tank changes.

2. The rubber member has a cylindrical main body portion having a rubber structure, a first connection portion provided at one end of the main body portion, and a second connection portion provided at the other end of the main body portion. The rubber member is attached to the lower wire guide at the first connection portion to close the opening provided at one end, and the second connection portion is disposed so as to surround the periphery of the opening of the machining tank and is attached to the machining tank, and closes the space between the inside of the cylinder of the rubber member and the inside of the machining tank where the machining fluid is stored. The wire electrical discharge machining apparatus according to claim 1, characterized in that.

3. The lower wire guide has a holding portion for holding the wire electrode, an insulating member attached to the lower arm for insulating between the holding portion and the lower arm, and a cylindrical intermediate member attached to the insulating member and through which the lower arm passes inside. The rubber member is characterized in that the first connection portion is connected to the intermediate member and the opening provided at one end is closed by the insulating member. The wire electrical discharge machining apparatus according to claim 2.

4. The lower arm has a flat upper surface, and the rubber member has a flat surface facing the flat upper surface of the lower arm. The wire electrical discharge machining apparatus according to any one of claims 1 to 3, characterized in that.

5. The lower arm has a rectangular cross-sectional shape, and the gib member has a square tube shape. The wire electrical discharge machining apparatus according to claim 4, characterized in that.

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