JPH08294825A - Wire electric discharge machine - Google Patents

Abstract

PURPOSE: To improve a work grade and work accuracy, prevent disconnection of a wire, and reduce work cost by inserting a wire electrode into guide holes formed in eccentric positions of dies, and eccentrically rotating the wire electrode by rotating the dies in a wire electric discharge machine. CONSTITUTION: A wire electrode 1 is introduced to a work object 2 by passing through an upper die 7, and is recovered by being also inserted into a lower die 8. Guide holes are bored in respectively eccentric positions in the upper die 7 and the lower die 8, and the wire electrode 1 is inserted into these guide holes. Since the upper die 7 and the lower die 8 are respectively driven in rotation by driving motors 13 and 15, the wire electrode 1 can eccentrically rotate according to the guide holes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine, and more particularly to a structure of a wire electrode traveling mechanism for machining a workpiece.

[0002]

2. Description of the Related Art In a conventional wire electric discharge machine, a wire electrode drawn from a supply drum is guided to a machining section through a guide roller and stretched in the machining section while maintaining a predetermined machining interval with a workpiece. Then, the work piece is processed by the discharge caused by the pulse voltage applied between the wire electrode and the work piece in the supplied working liquid.

In the wire electric discharge machining apparatus, a wire positioning die is arranged in front of and behind the machined portion for positioning, and the wire electrode insertion position is held while a predetermined tension is applied to the wire electrode. There is. In a usual electric discharge machine, in order to prevent vibration of the wire electrode and improve the positioning accuracy, many guide rollers are arranged before and after the machining portion and a large tension is applied to the wire electrode itself.

By the way, Japanese Patent Laid-Open No. 58-109228 discloses a technique for preventing the wire electrode from loosening or vibrating by twisting the wire electrode with a roller having a plurality of inclined shafts. In addition, JP-A 1-228
Japanese Patent Publication No. 729 discloses a technique of twisting a wire having a rectangular cross section to form a spiral wire electrode and improving sludge discharge characteristics.

[0005]

In the above-mentioned conventional wire electric discharge machine, as shown in FIG.
The processed groove 20 is formed in the workpiece 2 by the method. However, at the processed end 20a of the processed groove 20, the clearance with the surface of the wire electrode 1 is as small as 0.01 to 0.05 mm. It is difficult to supply a sufficient amount of working fluid, and it is also difficult to discharge sludge generated during working from within this interval. Therefore, due to insufficient circulation of the machining fluid and sludge retention, machining quality such as straightness of the machined surface and surface roughness, and deterioration of machining accuracy occur.

Further, in the wire electrode 1, a predetermined portion (a portion facing the processing end 20a) is worn out intensively. Therefore, especially when processing a thick work piece, depending on the wear shape of the wire electrode 1, the working quality and the working quality are improved. There is a possibility that the accuracy may deteriorate, and further, wire breakage may occur due to wear of the wire electrode 1. Especially when a large tension is applied to the wire electrode 1,
There is also a problem that an accident in which a wire electrode is disconnected due to the occurrence of secondary discharge due to sludge frequently occurs.

Further, in the techniques described in the above two documents, it is necessary to use a complicated roller mechanism and a strong wire tension in order to twist the wire electrode, or to make the wire have a rectangular cross section. In either case, there is a problem that the processing cost increases.

Therefore, the present invention solves the above-mentioned problems, and the problem is to improve the processing quality and processing accuracy by changing the traveling method of the wire electrode to improve the processing state in the processing portion. At the same time, it is intended to realize a structure capable of preventing a wire electrode cutting accident and to suppress the processing cost.

[0009]

A wire electric discharge machining apparatus according to the present invention is provided with a guide hole for inserting a wire electrode therein, and a pair of dies arranged before and after a machining section, and feeds the wire electrode in its extension direction. A wire running means and a rotation driving means for rotating the die are provided, and the rotation driving means is configured to rotate the die about an axis displaced from a position where the guide hole is formed. .

Here, the die is composed of an inner member having the guide hole formed at an eccentric position and an outer member having a fitting portion for eccentrically fitting and fixing the inner member. It is preferable that the member and the outer member are relatively rotatable.

It is preferable that at least one of the dice guide holes is inclined with respect to the wire electrode tension direction.

Further, it is preferable to provide a pressing means for applying a pressing force to the wire electrode in a direction intersecting the axial direction between the die and the processed portion.

Further, the torsional rotation speed of the wire electrode is set to a speed at which the processed end of the work piece can face the entire outer circumference of the wire electrode while the wire electrode passes through the work piece. Is preferred.

In this case, in particular, the twist rotation speed is S, the traveling speed of the wire is V, the thickness of the workpiece is D, and the wire electrode is processed without twisting. When the ratio of the worn area on the surface of the wire electrode is T, S ≧
It is desirable to set V (1-T) / D.

[0015]

According to the first aspect of the present invention, by rotating the die about the shaft center deviated from the position where the guide hole is formed,
Since the wire electrode inserted into the guide hole of the die rotates eccentrically, the eccentric rotation of the wire electrode allows the machining fluid to be supplied and discharged smoothly to the machining part, and also the sludge discharge is promoted. The state is stable, and the processing quality and processing accuracy can be improved.

According to the second aspect, the inner member and the outer member are made rotatable relative to each other, so that the eccentric amount of the guide hole with respect to the outer member can be changed only by rotating the inner member. The amount of eccentricity of the wire electrode can be easily adjusted. In this case, in particular, by making the eccentricity of the guide hole in the inner member the same as the eccentricity of the inner member fitted to the outer member, the eccentricity of both is canceled out depending on the rotational arrangement, and the eccentricity is reduced. Since it can be set to 0, it is possible to process the wire electrode without eccentricity.

According to the third aspect, the guide hole of at least one die is inclined with respect to the extending direction of the wire electrode, whereby the wire electrode can be eccentrically rotated and at the same time twisted and rotated. Therefore, the wear portion of the wire electrode can be rotated to make the wear degree uniform.

According to the fourth aspect, by providing the pressing means for applying a pressing force to the wire electrode in a direction intersecting the axial direction between the die and the processed portion, the guide hole and the wire electrode are provided. It is possible to prevent the deviation of the wire electrode due to the rotation of the die, which is caused by the clearance.

According to the fifth aspect, the twisting rotation speed of the wire electrode is set to a speed at which the processed end of the work piece can face the entire outer circumference of the wire electrode while the wire electrode passes through the work piece. By doing so, when the wire electrode passes through the workpiece, the entire outer circumference faces the working end and contributes to the discharge, so that the degree of wear on the outer circumference of the wire electrode can be made uniform.

According to claim 6, S ≧ V (1−T) / D
By doing so, the wire electrode is twisted and rotated once or more while passing through the workpiece, so that the degree of wear on the outer periphery of the wire electrode can be made uniform.

[0021]

Embodiments of the wire electric discharge machining apparatus according to the present invention will be described below with reference to the drawings. [Embodiment 1] In Embodiment 1, as shown in FIG. 1, the wire electrode 1 pulled out from the supply drum 3 is inserted into the upper die 7 through the guide rollers 4, 5, 6 to be processed. After passing through the processing section where 2 is arranged, lower die 8
Has been inserted into. The wire electrode 1 exiting the lower die 8 is guided to the waste container 12 via the guide rollers 9, 10, 11.

The upper die 7 is rotationally driven by the drive motor 13 via the drive belt 14, and the lower die 8 is rotationally driven by the drive motor 15 via the drive belt 16.

FIG. 2 is a plan view showing the structures of the upper die 7 and the lower die 8. Upper die 7 and lower die 8
Is a hard metal disc having a cylindrical outer peripheral surface, and the guide hole 7 is provided at a position eccentric from the center O by a predetermined distance.
a and 8a are formed. The amount of eccentricity varies depending on the size of the work piece and the device, but generally, when the wire diameter is 0.05 to 0.25 mm, the distance between the center O of the die and the centers of the guide holes 7a and 8a is small. 0.01-0.15 mm
It is set to a degree.

Between the axis of the guide hole 7a of the upper die 7 and the wire installation position of the guide roller 6, and the lower die 8
There is a predetermined distance L between the axis of the guide hole 8a and the installation position of the guide roller 9, and this distance L is
Due to the eccentricity of the guide holes 7a, 8a, it is set larger than the distance that the axis moves.

According to this embodiment, the drive motors 13 and 15 are operated to rotate the upper die 7 and the lower die 8 while the wire electrode 1 is running with a predetermined tension applied from the supply roller. The wire electrode 1 has guide holes 7 around the center of rotation of the upper die 7 and the lower die 8.
It is eccentrically rotated so as to turn by the amount of eccentricity of a and 8a. The state of this eccentric rotation is shown in FIG.

When the wire electrode 1 is eccentrically rotated by a predetermined amount of eccentricity, the machining liquid in the machining groove 20 of the workpiece 2 moves according to the rotation direction of the wire electrode as indicated by the arrow in the figure, so that the machining end is processed. The supply and discharge of the machining liquid to the 20a are promoted, the sludge is smoothly discharged, and the machining speed and the machining condition are stabilized, so that the machining quality and the machining accuracy are improved, and the secondary discharge caused by the sludge, etc. It is possible to prevent the wire from breaking due to the cause of.

By rotating the upper die 7 and the lower die 8 in synchronization with each other, the wire electrode 1 can be stably eccentrically rotated. The eccentric rotation by the die slightly twists the wire electrode 1 itself, so that the looseness and vibration of the wire electrode 1 are reduced and the portion of the wire electrode 1 facing the processed end 20a is sequentially rotated.
This has the effect of making the degree of wear of the wire electrode 1 uniform in the circumferential direction. The amount of twist of the wire electrode 1 varies depending on the clearance between the die and the wire electrode and the frictional resistance.

In the above embodiment, the upper die 7 and the lower die 8 may be rotated in different phases.
It is possible to rotate at different rotation speeds or in different directions. In these cases, the twisting of the wire electrode 1 can be promoted, and the running stability of the wire electrode 1 and the averaging of the degree of wear can be further improved.

The distance L between the guide rollers 6 and 9 and the upper and lower dies is more accurately defined as the sum of the eccentric amount of the guide holes 7a and 8a of the die and the clearance amount of the guide holes 7a and 8a with respect to the wire electrode 1. It is set large. Therefore, even if the wire electrode 1 is eccentrically rotated as described above, the wire electrode 1 is always attracted toward the guide rollers 6, 9 and is amplified by the eccentric rotation due to the clearance required for the guide holes 7a, 8a. It is possible to prevent the wire electrode from being shaken.

The upper die and the lower die are
It is supported by being rotatably attached to a support arm member (not shown) via a bearing.

[Second Embodiment] Next, a second embodiment of the wire electric discharge machining apparatus according to the present invention will be described. The second embodiment has the same basic structure as the first embodiment, but the structures of the upper die 7 and the lower die 8 are slightly different. FIG. 4 is a cross-sectional view showing the structure of the die 17 used in the second embodiment.

The die 17 is composed of an inner member 18 and an outer member 19, and the inner member 18 is fitted into an eccentric hole 19a formed in the outer member 19. Inner member 18
The fitting portion between the outer member 19 and the outer member 19 is rotatable, and the inner member 18 and the outer member 19 are separately fixed to a base (not shown) by bolts or the like.

A guide hole 18a is formed in the inner member 18 at a position eccentric from the center Q thereof, and the wire electrode 1 is inserted into the guide hole 18a. The guide hole 18a has a center R of the outer member 19 in the illustrated case.
Is arranged concentrically with the inner member 18 and the outer member 1
By rotating and fixing a predetermined amount with respect to 9 from the state shown in the figure, it is possible to dispose the outer member 19 so as to be eccentric from the center R of the outer member 19 by a predetermined amount as shown by a dotted line. This amount of eccentricity can be increased or decreased by rotating the inner member 18.

The eccentric amount of the eccentric hole 19a of the outer member 19,
The eccentric amount of the guide hole 18a of the inner member 18 can be set arbitrarily, but as in the above embodiment, the eccentric hole 19a can be set.
By making the eccentricity of a equal to the eccentricity of the guide hole 18a, the eccentricity of the guide hole 18a with respect to the center R of the outer member 19 can be made zero depending on the rotation position of the inner member 18, and It is possible to prevent the wire electrode 1 from swinging when the die 17 is rotated.

The fitting and fixing structure between the inner member and the outer member is not only the indirect fixing structure by fixing to the common base as described above, but also the eccentric hole 19a and the inner member 18. Engraving a large number of teeth corresponding to each other on the outer circumference,
Known means such as a structure for engaging and fixing these can be used.

[Third Embodiment] Next, a third embodiment according to the present invention.
Will be explained. This embodiment basically has the same configuration as that of the first embodiment. However, by using the lower die of Example 1 as the lower die 21 having the guide hole 21a inclined with respect to the axis of the wire electrode 1 as shown in FIG. A twist can be added to the electrode 1.

In this embodiment, the guide hole 21a of the lower die 21 is inclined so that the wire electrode 1 is eccentrically rotated in the same manner as in each of the above-described embodiments, and the wire electrode 1 is substantially synchronized with the rotation of the lower die 21. Since the twist can be surely imparted, the machining can be performed while sequentially changing the portion of the machining portion where the wire electrode 1 faces the machining end of the workpiece. Therefore, by adjusting the rotation speed of the lower die 21, the electric discharge machining can always be continued at a new portion of the wire electrode 1, the machining state can be stabilized, and the machining accuracy can be improved.

In the present embodiment, when there is a clearance between the guide hole 21a of the lower die 21 and the wire electrode 1, the wire electrode 1 is twisted, so that one of the guide holes 21a is always provided. In the approached state, the swing width changes by the clearance. However, by moving the guide roller 22 shown in FIG. 5 in accordance with the eccentric rotation of the wire electrode 1, the eccentrically rotating wire electrode 1 is constantly pressed in a predetermined direction (right direction in FIG. 5), and the swing width is reduced. It is possible to match the amount of eccentricity of the opening of the guide hole 21a.

The guide roller 22 is slidably fitted to the X-direction guide portion 23a formed on the upper portion of the base 23.
The direction moving table 24 and the Y direction moving table 25 slidably fitted to the Y direction guide portion 24a formed on the X direction moving table 24 are supported so as to be movable in both XY directions. These moving bases synchronize with the eccentric rotation of the wire electrode 1 so as to accurately follow the wire electrode 1,
It is driven by a hydraulic drive system, an air pressure drive system, or the like.

The lower die 21 of this embodiment is rotatably supported by a support member (not shown) via a bearing.

[Fourth Embodiment] Next, a fourth embodiment according to the present invention.
Will be described. In the fourth embodiment, the upper die of the third embodiment has a die structure similar to that of the lower die 21. A guide roller similar to the guide roller 22 is also provided between the upper die and the processing section. By doing so, when the upper die and the lower die are respectively rotated synchronously, when the phase is changed with respect to the formation position of the guide hole, when rotated, when the rotational speed is changed, and when rotated in different directions. , Different eccentric rotation states and torsional rotation states can be expressed.

[Fifth Embodiment] Next, a fifth embodiment according to the present invention.
Will be described. In the fifth embodiment, in addition to the basic configuration of the first embodiment, a twisting roller 28 that is rotatable around an axis parallel to the axial direction of the wire electrode 1 is provided under the lower die 8 and the twisting roller 28 is used. The roller 28 is configured to be rotated by the drive motor 27. For the twisting roller 28, the wire roller 1 is sandwiched between the pressing roller 29 and the pressing roller 29.
Are arranged so as to face each other, and due to these configurations, the wire electrode 1 is forcibly twisted and rotated.

When the wire electrode 1 is twisted and rotated by the structure shown in each of the above-described embodiments, the twisting rotation speed is set so that the new discharge surface is always directed to the machining end of the workpiece.
By adjusting for the traveling speed of, a more stable machining state is realized in the machining section, and machining quality and machining accuracy can be improved. In addition, since the discharge is performed on the entire outer periphery of the wire electrode 1 on average, damage to the wire can be prevented, the life of the wire can be extended and reused, and at the same time, breakage of the wire can occur. Since it can be avoided, the accident rate can be reduced. Therefore, the processing cost can be suppressed as a whole.

When the twisting rotation of the wire electrode 1 is performed almost in synchronism with the rotation of the die, more effective processing can be performed by setting the rotation speed of the die as follows. .

That is, in the case of rough machining (processing for roughly forming the entire shape), if the machining is performed without twisting and rotating, about 2/3 of the outer circumference of the wire will be worn. age,

When finish processing (processing for re-tracing the surface of the processed portion to improve smoothness and dimensional accuracy) is performed without twisting and rotating, about 1/4 of the wire outer circumference is worn. From that, And

When the rotation of the die and the rotation of the wire are not synchronized, the actual twisting rotation speed of the wire electrode is measured, and the twisting rotation speed is calculated by the above formula (1) or (2). The desired effect can be obtained by experimentally setting the rotation speed of the die so that the rotation speed becomes.

The above expressions (1) and (2) show the minimum rotation speed, and the rotation speed may be higher than the rotation speed obtained by these expressions. For example, if the rotation speed is twice as high as the above expression, the part of the wire electrode that is once worn will be machined again, but the degree of wear will be 2
Since it is doubled, it becomes 1/2, so that the final degree of wear is the same, and since the rotation speed becomes high, the uniformity of wear is rather improved.

In order to make the above equation easier to understand, description will be given using actual numerical values. For example, the workpiece has a thickness of 50 mm
And the wire traveling speed is 8000 mm / min in rough machining, and the wire traveling speed is 6000 mm / min in finishing machining.
The rotation speeds of the above formulas (1) and (2) are as shown in Table 1 below.

[0050]

[Table 1] Workpiece thickness Minimum rotation speed (rough cutting) Minimum rotation speed (finishing) 50mm 53 / min 90 / min 20mm 133 / min 225 / min

By imparting a twist rotation having a predetermined rotation speed to the wire electrode in this manner, the degree of wire wear can be surely made uniform, so that the degree of damage of the wire as a whole can be greatly reduced. Therefore, the traveling speed of the wire can be suppressed, the wire can be reused, and the consumption of the wire can be reduced.

[0052]

As described above, according to the present invention,
By rotating the die about an axis that is displaced from the position where the guide hole is formed, the wire electrode inserted into the guide hole of the die rotates eccentrically. Since the supply and the discharge are smoothly performed and the discharge of the sludge is promoted, the processing state is stable, and the processing quality and the processing accuracy can be improved. Since this method does not require a complicated guide mechanism or a special wire shape, it is possible to perform high-quality processing without increasing the processing cost. It is also possible to prevent local wear of the wire and disconnection of the wire due to sludge.

In particular, since the wear of the wire can be made uniform by applying the twist rotation to the wire electrode, the traveling speed of the wire electrode can be reduced.
The consumption of the wire can be reduced because the wire can be reused.

Since the risk of wire breakage can be avoided as described above, it is possible to use thin wires.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a wire electric discharge machining apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a structure of a die according to the first embodiment.

3A and 3B are a cross-sectional view (a) of a machined part and a cross-sectional view (b) of the machined part of Example 1 for showing a machining state of conventional wire electric discharge machining.

FIG. 4 is a cross-sectional view showing the structure of a die of Example 2 of the wire electric discharge machining apparatus according to the present invention.

FIG. 5 is a cross-sectional view showing a structure of a lower die of a wire electric discharge machining apparatus according to a third embodiment of the present invention.

FIG. 6 is a schematic configuration diagram showing a structure near a lower die of a wire electric discharge machining apparatus according to a fifth embodiment of the present invention.

[Explanation of symbols]

 1 Wire Electrode 2 Workpiece 7 Upper Die 8 Lower Die 13,15 Drive Motor

Claims (6)

[Claims] 1. A pair of dies, each of which has a guide hole for inserting a wire electrode and is arranged in front of and behind a processing portion, a wire running means for feeding the wire electrode in its extension direction, and a rotation driving means for rotating the die. And the rotation driving means is configured to rotate the die about an axis displaced from the position where the guide hole is formed. 2. The die according to claim 1, wherein the die comprises an inner member having the guide hole formed at an eccentric position, and an outer member having a fitting portion for eccentrically fitting and fixing the inner member. A wire electric discharge machine, wherein the inner member and the outer member are configured to be rotatable relative to each other. 3. The wire electric discharge machine according to claim 1, wherein the guide hole of at least one of the dies is inclined with respect to the extending direction of the wire electrode. 4. The pressing device according to claim 1, further comprising: a pressing unit that applies a pressing force to the wire electrode in a direction intersecting the axial direction between the die and the processing unit. Wire electric discharge machine. 5. The twisting rotation speed of the wire electrode according to claim 1 or 3, wherein a processing end of the work piece is provided on an entire outer circumference of the wire electrode while the wire electrode passes through the work piece. The wire electric discharge machine is characterized in that the speed is set so that the two can face each other. 6. The method according to claim 5, wherein the twist rotation speed is S, the traveling speed of the wire is V, the thickness of the workpiece is D, and the wire electrode is processed without twisting. If the ratio of the worn area on the surface of the wire electrode is T, then S ≧
V (1-T) / D The wire electric discharge machine characterized by the above-mentioned.