JPH09207030A - Electric discharge machining method and apparatus - Google Patents

Abstract

(57) [Abstract] [Problem] To apply high-efficiency machining of a free-form surface by applying a wire electric discharge machining technique. SOLUTION: A wire electrode 1 drawn from a bobbin 15
1 is sent to the wire feeding device 13 and the wire drawing device 14 by the wire supplying device 12, and the wire electrode 11 is deformed with a predetermined curvature by the roller group in both devices 13 and 14, and the curved shape part having a predetermined radius of curvature. 11a is formed, and the curved-shaped portion 11a of the wire electrode is brought close to the workpiece W placed on the X-axis table 4 and the Y-axis table 5 to generate an electric discharge between the two, thereby continuously connecting the wire electrode 11 to each other. The curved shape portion 11a is bitten into the workpiece W while being fed, and a part thereof is cut out. If necessary, the interval between the wire feeding device 13 and the wire drawing device 14 and the roller position of each roller group are changed. Curved portion 1 of wire electrode 11
Processing is advanced by changing the shape and size of 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical discharge machining method, and more particularly to an electrical discharge machining method and apparatus suitable for machining a free curved surface such as a die.

[0002]

2. Description of the Related Art Cutting of a free-form surface such as a die is generally performed by cutting with a ball end mill or the like, but recently, since it can be processed regardless of hardness and there is no restriction on the processed shape, Electric discharge machining has come into wide use. Conventionally, in order to machine a free-form surface by electric discharge machining, a block-shaped electrode having a tip shape that is the inverse of the target machining shape has been used. Although electric discharge is generated in the and the engraving is gradually performed, it has a drawback that the processing speed is generally slow.

By the way, recently, for the purpose of locally cutting out a defective portion having a crack or a blowhole, a curved electrode is used as a discharge electrode, and a swinging motion is applied to this electrode to cut out a workpiece. A method has been proposed (Actual Kaihei 2-15
It is considered that if this method is applied to the processing of the free curved surface, a large lump can be cut out at one time, and the processing of a mold or the like can be performed with high efficiency.

[0004]

However, according to the electric discharge machining method described in the above publication, since the molded body is used as the curved electrode, the consumption of the electrode is inevitable and the desired accuracy is ensured. Has a problem that the machining efficiency cannot be improved as expected, because the machining must be performed under low wear conditions (low current value) with low machining efficiency or the electrodes must be frequently replaced.

The present invention has been made in view of the above-mentioned problems of the prior art, and its problem is that wire electric discharge machining (wire cutting) conventionally used for machining (cutting) of a two-dimensional contour shape. The purpose of this technology is to make it possible to process free-form surfaces with high efficiency.

[0006]

In order to solve the above-mentioned problems, the method and apparatus of the present invention are such that the wire electrode sent by the wire supplying means is deformed into a predetermined curved shape by the deforming means, and the wire electrode is bent. It is characterized in that the shape portion is used as an electric discharge portion for processing a workpiece.

In the electric discharge machining method and apparatus thus constructed, the curved surface of the wire electrode and the workpiece are moved relatively to each other, whereby the curved surface can machine a free-form surface. At this time, by feeding the electrode wire continuously or intermittently, it is possible to process without considering the electrode consumption.

In this case, the curved portion of the wire electrode may be arbitrarily changed by the shape changing means, whereby the working width and the working depth can be adjusted to improve the working efficiency and working accuracy. .

In the apparatus of the present invention, the shape changing means is arranged from the distance changing means for relatively moving the wire feeding portion and the wire drawing portion to change the distance between the wire feeding portion and the wire drawing portion, or in the wire feeding portion and the wire drawing portion, respectively. In addition, a curvature changing unit that arbitrarily changes the curvature of the wire electrode may be provided. By changing the distance between the wire feeding portion and the wire retracting portion by the distance changing means, or by changing the curvature of the wire electrode by the curvature changing means, the degree of freedom in changing the shape of the curved shape portion of the wire electrode is increased. Become. In this case, the curvature changing means is composed of a roller group having at least three rollers, and
Of the two rollers, one roller located on the payout end side of the wire payout part and one located on the drawin end side of the wire draw-in part
The book roller may be arranged so as to be movable in the relative movement direction of the wire feeding portion and the wire drawing portion, and this makes it possible to easily change the curvature of the wire electrode.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIGS. 1 to 4, reference numeral 1 denotes a U-shaped machine body in which a bottom base 2 and an upper beam 3 are arranged on opposite sides of the U-shape, and a workpiece W is placed on the bottom base 2. An X-axis table 4 and a Y-axis table 5 for mounting are arranged in a superposed state. The X-axis table 4 is movably connected to the Y-axis table 5 in the X-axis direction (left and right direction in FIG. 1), and the Y-axis table 5 is connected to the bottom base 2 in the Y-axis direction (paper surface in FIG. 1). Is vertically movably connected to each other, and each of them is connected to the X-axis by the operation of the motors 6 and 7.
It is designed to be driven in the axial direction and the Y-axis direction.

The upper beam 3 of the machine body 1 is provided with a Z-axis shaft 8 which is vertically driven by a driving means (not shown), and the lower end of the Z-axis shaft 8 has a driving means (not shown). A supporting frame 10 is attached via a C-axis disk 9 which is rotationally driven by (1). On the upper side of the support frame 10, a wire supply device 12 for sending and collecting the wire electrode 11 is arranged, while on the lower side of the support frame 10, a wire feeding device (wire feeding device for feeding the wire electrode 11). A wire drawing unit 13 and a wire drawing device (wire drawing unit) 14 for drawing the wire electrode 11 drawn from the wire drawing device 13 are arranged in parallel with respect to the workpiece W.
Regarding the wire feeding device 13 and the wire drawing device 14,
Details will be described later.

The wire supply device 12 is provided with roller pairs 12a and 12b which are rotatably driven by respective independent driving means (not shown), and the wire electrode 11 is provided with the roller pairs 12a and 12b.
The portion b is extended in a state of frictional contact with the roller surface. The wire electrode 11 is drawn out from the supply bobbin 15 arranged at the upper corner of the machine body 1 along the upper beam 3 and is changed in direction by about 90 degrees by the first deflecting roller 16 provided on the upper beam 3 to supply the wire. It is introduced into the wire 12, and is sent to the wire feeding device 13 by the rotational force of the one roller pair 12a. The wire electrode 11 drawn out from the wire drawing-out device 13 is U-turned in a predetermined curved shape at a position facing the workpiece W on the X-axis table 4 and drawn into the wire drawing-in device 14,
It is sent upward by the rotational force of the other roller pair 12b in the wire supply device 12 and is changed in direction by approximately 90 degrees by the second deflecting roller 17 provided on the upper beam 3, and further passes through the recovery roller pair 18 and then the machine body 1 It is designed to be collected in a collecting container 19 adjacent to. Here, the left and right roller pairs 12a and 12b of the wire supply device 12 rotate at the same speed in synchronization with each other during electric discharge machining. Therefore, the wire electrode 11 and the wire feeding device 13 are rotated. A predetermined curved shape is maintained with the wire retracting device 14.

On the other hand, the wire feeding device 12 and the wire feeding device
In the area between 13 and the wire retractor 14,
Power supply terminals 22a and 22b connected to the power supply terminals 20 and 22 via wiring 21 are provided, and power is supplied to the wire electrode 11 through these power supply terminals 22a and 22b. Further, the workpiece W is also connected to the power supply device 20 via the wiring 23,
Therefore, while the electric power is being supplied from the power supply device 20 to the wire electrode 11, the curved portion 11a of the wire electrode 11 between the wire feeding device 13 and the wire drawing device 14 is moved to the workpiece W by the extension operation of the Z-axis shaft 8. The curved part
A voltage is applied between 11a and the workpiece W to generate an electric discharge, and the energy of the electric discharge gradually engraves the workpiece W. In the actual electric discharge machining, the machining tank 25 containing the machining liquid 24 is installed on the X-axis table 4, and the workpiece W is immersed in the machining liquid 24 in the machining tank 25 to perform the electric discharge machining. Then, the flow of the working fluid 24 is used to remove the processing waste.

As shown in FIGS. 2 to 4, the wire feeding device 13 has a first roller consisting of three rollers 26A, 26B and 26C.
The roller group 26 of the wire drawing device 14 is composed of four rollers.
A second roller group 27 including 27A, 27B, 27C and 27D is provided, respectively. The wire electrode 11 sent by the wire supply device 12 is deformed from a linear state to a predetermined curvature while passing between the rollers of the first roller group 26, while the wire electrode 11 is fed from the wire feeding device 13. The electrode 11 is deformed from a curved state having a predetermined curvature to a linear state while passing between the rollers of the second roller group 27, and as a result, between the wire feeding device 13 and the wire drawing device 14. Wire electrode
11 has a predetermined curved shape (curved shape portion 11a).

The first and second roller groups 26 and 27 shown in FIG.
As shown in FIG. 3, the movable plates (space changing means) 28 and 29 are mounted on the support frame 10 so as to be movable in the X-axis direction. The movable plates 28 and 29 are screwed to a pair of left and right screw rods 31 and 32, which are rotationally driven by a motor 30 arranged in the center of the support frame 10 in the width direction, via nuts (not shown). The screw rods 31 and 32 have mutually opposite screw directions. Therefore, when the screw rods 31 and 32 are rotated in the same direction by the operation of the motor 30, the movable plate 28 and the movable plate 29 are separated from each other by X. The relative movement in the axial direction allows the distance between the first roller group 26 and the second roller group 27, that is, the distance between the wire feeding device 13 and the wire drawing device 14 to be arbitrarily changed.

On the other hand, 3 constituting the first roller group 26
Of the rollers 26A to 26C, the roller 26C located on the feeding end side of the wire electrode 11 and outside thereof, and the four rollers 27A to 27D forming the second roller group 27, of the wire electrode 11 Roller 27A located on the retracted end side and outside thereof
Are arranged on sub movable plates (curvature changing means) 33, 34 mounted on the movable plates 29, 30 so as to be movable in the X-axis direction.

The sub movable plates 33, 34 are screw rods which are rotationally driven by motors 35, 36 fixed to the side surfaces of the movable plates 28, 29.
It is screwed to 37, 38 via a nut (not shown). Therefore, the screw rods 37, 38 are now activated by the operation of the motors 35, 36.
When is rotated, the movable plate 2 to which the sub movable plates 33 and 34 correspond
By moving the rollers 8 and 29 in the X-axis direction and changing the positions of the rollers 26C and 27A with respect to the adjacent fixed rollers 26B, 26A, 27B and 27C, the wire feeding angle and the drawing angle are changed. Accordingly, the curvature of the wire electrode 11 drawn from the wire drawing device 13 and the curvature of the wire electrode 11 drawn into the wire drawing device 14 are changed. Therefore, the two motors 35 and 36 are designed to be operated in synchronization with each other, whereby the roller 26C and the roller 27 are driven.
The wire electrode 11 moves relative to A in the X-axis direction, and the wire electrode 11 undergoes bending deformation at the same curvature at the pay-out end of the wire pay-out device 13 and the draw-in end of the wire draw-in device 14. The second roller group
Out of 27, the roller 27D on the most exit side of the wire retractor 14
Is useful for straightening the wire electrode 11, and
Since it is not directly involved in the shape setting of a, this can be omitted. Also, the two motors 35 and 36 can be operated asynchronously.

Here, the curved shape portion 11 of the wire electrode 11 is
A specific operation for changing the shape and size of a will be described with reference to FIGS. FIG. 5 shows a case where the curved portion 11a of the wire electrode 11 is formed in a semicircular shape and its radius of curvature is changed. In the figure,
The shape shown in the center represents a standard shape, and when the radius of curvature is made larger than this, the movable plates 28 and 29 are moved in a direction away from each other by the operation of the motor 30 (FIG. 2), The first roller group 26 and the second roller group 26
The distance between the roller group 27 and the roller group 27 is increased. At the same time, the motors 35 and 36 (FIG. 2) are operated in synchronization to operate the wire feeding device.
The auxiliary movable plate 33 on the 13 side and the auxiliary movable plate 34 on the wire retracting device 14 side are moved in a direction in which they are separated from each other, and as shown by the black arrow, the roller 26C on the wire feeding end side and the wire retracting end side. The rollers 27A of the wire electrode 11 respectively
Move it to the outside of 11a by a specified distance.

On the other hand, when the radius of curvature is made smaller than that of the standard shape shown in FIG. 5, the movable plates 28 and 29 are moved toward each other by the operation of the motor 30, as indicated by the white arrow. The distance between the first roller group 26 and the second roller group 27 is narrowed. At the same time, the motors 35 and 36 are operated in synchronization to move the auxiliary movable plate 33 on the wire feeding device 13 side and the auxiliary movable plate 34 on the wire retracting device 14 side in a direction in which they approach each other. As shown by the line arrow, the roller 26C on the wire feeding end side and the roller 27A on the wire drawing end side are moved to the inside of the curved portion 11a of the wire electrode 11 by a predetermined distance.

That is, the curved portion 11a of the wire electrode 11
If you want to change the radius of curvature with a semicircle,
The relative movement direction of the roller group 26 and the second roller group 27, and the relative movement direction of the wire feeding end side roller 26C and the wire drawing end side roller 27A are the same. Wire electrode 11
In order to make the curved shape portion 11a of the above-mentioned semi-circular shape, it is sufficient to adjust the feeding amount of the wire electrode 11 in accordance with the interval between the first roller group 26 and the second roller group 27 described above. Is
The rotation can be performed by making the rotational speeds of the left and right roller pairs 12a and 12b of the wire supply device 12 different from each other, or by rotating them in opposite directions. In this way, once the curved shape portion 11
If a is set to a semi-circle, its shape will be stable, and the pair of rollers 12a and 12b on the left and right of the wire supply device 12 will rotate at the same speed during electric discharge machining, so that the wire electrode 11 is continuously supplied. However, the curved shape does not collapse.

FIG. 6 shows a case where the protruding height and width of the curved portion 11a of the wire electrode 11 are changed. In the same figure, the shape shown at the center represents a standard shape, and when the protruding height (processing depth) of the curved shape part 11a is made smaller (shallow) and the protruding width (processing width) is made wider than this. Is moved by the operation of the motor 30 in a direction in which the movable plates 28 and 29 are separated from each other, and the distance between the first roller group 26 and the second roller group 27 is increased as indicated by the white arrow. Expanding. At the same time, the motors 35 and 36 are operated in synchronization to move the auxiliary movable plate 33 on the wire feeding device 13 side and the auxiliary movable plate 34 on the wire retracting device 14 side in a direction in which they approach each other. As shown by the line arrow, the roller 26C on the wire feeding end side and the roller 27A on the drawing end side are moved to the inside of the curved portion 11a of the wire electrode 11 by a predetermined distance.

On the other hand, when the protrusion height from the standard shape of FIG. 6 is increased (the machining depth is increased) and the protrusion width (machining width) is narrowed, the movable plate 28 is operated by the operation of the motor 30.
And 29 are moved toward each other to reduce the distance between the first roller group 26 and the second roller group 27 as indicated by the white arrow. At the same time, the motors 35 and 36 are operated in synchronism to move the auxiliary movable plate 33 on the wire feeding device 13 side and the auxiliary movable plate 34 on the wire drawing device 14 side in the direction in which they are separated from each other. As indicated by the line arrow, the roller 26C on the feeding end side and the roller 27A on the drawing end side are moved to the outside of the curved portion 11a of the wire electrode 11 by a predetermined distance.

That is, when the protruding height and width of the curved portion 11a are changed, the relative movement direction of the first roller group 26 and the second roller group 27, and the wire feeding end side roller 26C and the wire. The relative movement direction with respect to the roller 27A on the retracted end side is opposite. However, in this case, the radius of curvature of the curved portion 11a of the wire electrode 11 does not become uniform within the arc, but changes depending on the part.

In the present embodiment, the driving motor 6 for the X-axis table 4 and the driving motor 7, Z for the Y-axis table 5 are used.
A motor for driving the shaft 8 (not shown), a motor for driving the C-axis disc 9 (not shown), a motor for driving the pair of left and right rollers 22a, 22b of the wire supply device 12 (not shown), the first and A motor 30 for relative movement of the second roller groups 26 and 27, a roller 26C on the wire feeding end side, and a roller 27A on the drawing end side.
The operations of the relative movement motors 35 and 36 are controlled by a numerical controller (NC). In the electric discharge machining, the curved shape portion 11a of the wire electrode 11 between the wire feeding device 13 and the wire drawing device 14 is previously set to a predetermined shape and size by the operation of the motors 30, 35, 36 and the like.

Then, the wire electrode 11 is continuously sent at a predetermined speed by the operation of the wire supply device 12, and the power supply device is also provided.
Electric power is supplied from 20 to the wire electrode 11 and the workpiece W to apply a voltage between them, so that the curved portion 11 of the wire electrode 11
By the relative movement of a and the workpiece W, the curved shape portion 11a is gradually bitten into the workpiece W while causing an electric discharge between the two, and the curved shape portion 11a is moved along a predetermined locus to be processed. Cut out a lump of a predetermined size from the object W. When one lump is cut out in this way, the curved shape portion of the wire electrode 11 is formed so that the cut mark (working surface) is overlapped with the next cut mark.
11a is moved, the next block is cut out, and this is repeated at a predetermined pitch to finish the predetermined engraving.

In the above-mentioned die engraving, it is usual to carry out two-step processing including roughing and finishing, and when performing roughing, the machining efficiency is emphasized and, for example, as shown in FIG. Processing is performed by increasing the radius of curvature of the curved portion 11a of 11 and increasing the current value supplied from the power supply device 20 to the wire electrode 11. Further, when processing a deep shape, as shown in FIG. 6, the protruding height of the curved shape portion 11a is increased to perform the processing. On the other hand, when finishing is performed, the shape accuracy and the surface accuracy are emphasized and, for example, as shown in FIG.
As shown in FIG. 6, the radius of curvature of the curved portion 11a is reduced, or as shown in FIG. 6, the shape has a horizontally long arc, and the current value supplied from the power supply device 20 to the wire electrode 11 is reduced. I do. In particular, as shown in FIG. 6, when the shape has a horizontally long arc, it is possible to improve the surface quality by lowering the height of the caps in addition to increasing the processing range by increasing the range of processing at one time. You can The shape and size of the curved portion 11a of the wire electrode 11 are changed by the relative movement between the first roller group 26 and the second roller group 27 and the roller 26C on the wire feeding end side as described above. It is performed by relative movement with the roller 27A on the wire pull-in end side, but by changing the changing time, changing shape and the like in the NC control device in advance, the shape and size of the curved shape portion 11a can be changed during processing. By doing so, it becomes possible to proceed with the processing with almost no interruption.

In the present invention, in principle, the wire electrode 11 is continuously supplied to eliminate electrode consumption. However, when the protruding height of the curved portion 11a is increased as shown in FIG. The continuous supply of 11 may displace the tip end position of the curved portion 11a in the left-right direction. in this case,
The feed of the wire electrode 11 is interrupted during the electric discharge machining, the electric discharge machining is interrupted at a timing when the electrode wear does not progress so much, and the wire electrode 11 of the curved portion 11a is replaced. That is, it is possible to realize electric discharge machining which is not affected by electrode wear by intermittently sending the wire electrode.

In the above embodiment, each of the wire feeding device 13 and the wire drawing device 14 includes a roller group.
However, instead of the roller group, they may have a simple nozzle shape. In this case, a movable plate as a means for changing the distance between the wire feeding part and the wire drawing part. It is possible to arbitrarily change the curved shape portion 11a of the wire electrode 11 by moving the wires 28 and 29 relative to each other by the motor 30 and changing the amount of extension of the wire electrode 11. Further, the present invention provides the space changing means (movable plates 28, 29, etc.) or the curvature changing means (roller group) as means for arbitrarily changing the curved portion 11a of the wire electrode 11.
26, 27, auxiliary movable plates 33, 34, etc.) may be independently provided at positions apart from the wire feeding portion and the wire drawing portion.

[0030]

According to the electric discharge machining method and apparatus according to the present invention, a free-form surface can be machined in the manner of wire cutting, so that it is possible to machine a deep drawing die with high efficiency. is there. It is also possible to arbitrarily change the curved shape of the wire electrode, and in this case, it is possible to perform processing under optimum conditions that match the processing shape and processing accuracy.

[Brief description of drawings]

FIG. 1 is a side view schematically showing the overall structure of an electric discharge machine according to the present invention.

FIG. 2 is a side view showing a structure of a wire feeding part and a wire drawing part of the electric discharge machine.

FIG. 3 is a perspective view showing an arrangement state of a roller group of a wire feeding portion.

FIG. 4 is a perspective view showing an arrangement state of a roller group of a wire pull-in portion.

FIG. 5 is a schematic diagram showing the movement of a roller group for changing the curved shape of a wire electrode.

FIG. 6 is a schematic diagram showing another movement of the roller group for changing the curved shape of the wire electrode.

[Explanation of symbols]

 1 Aircraft 4 X-axis table 5 Y-axis table 8 Z-axis shaft 9 C-axis disk 11 Wire electrode 12 Wire supply device 13 Wire feeding device (wire feeding part) 14 Wire drawing device (wire drawing part) 20 Power supply device 26 1st Roller group 27 Second roller group 26A-26C Rollers 27A-27D Rollers 28,29 Movable plate (space change means) 33,34 Sub-movable plate (curvature change means) W Workpiece

Claims (7)

[Claims] 1. A wire electrode sent by a wire supplying means is deformed into a predetermined curved shape, and the curved shape portion of the wire electrode is used as an electric discharge portion for processing a workpiece to perform electric discharge machining. Characteristic electrical discharge machining method. 2. The electric discharge machining method according to claim 1, wherein the curved portion of the wire electrode is arbitrarily changed. 3. Deformation means for deforming the wire electrode sent by the wire supply means into a predetermined curved shape is provided, and the curved shape portion of the wire electrode is used as an electric discharge portion for processing a workpiece. An electric discharge machine characterized by the above. 4. The electric discharge machine according to claim 3, further comprising shape changing means for arbitrarily changing the curved shape of the wire electrode. 5. The electric discharge machining apparatus according to claim 4, wherein the shape changing unit includes a space changing unit that relatively moves the wire feeding unit and the wire drawing unit to change the distance between them. . 6. The discharge according to claim 4, wherein the shape changing means is provided in each of the wire feeding portion and the wire drawing portion, and includes curvature changing means for arbitrarily changing the curvature of the wire electrode. Processing equipment. 7. The curvature changing means is made up of a group of rollers having at least three rollers, and at least one roller of the three rollers is located on the payout end side of the wire payout section, and a wire pull-in section. 7. The electric discharge machining apparatus according to claim 6, wherein the one roller located on the pull-in end side is disposed so as to be movable relative to the other rollers.