JP3057906B2 - Wire electric discharge machining method - Google Patents

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 machining method, and more particularly, to a wire electric discharge machining method which prevents vibration or fluttering of a wire electrode at an early stage of electric discharge machining.

[0002]

2. Description of the Related Art In general, a wire electric discharge machine is used as a device for cutting a workpiece by applying a predetermined voltage to a wire electrode to be fed to generate a discharge phenomenon between the wire electrode and the workpiece. Is already known. This type of wire electric discharge machine has a machining head 2 which can be moved up and down, for example, as shown in FIG. 5, and a V-axis moving mechanism for exerting a taper function at the lower end of the machining head 2. 4 and V
A U-axis moving mechanism 6 that moves in a U-axis direction orthogonal to the axis is attached. The U-axis moving mechanism 6 is provided with an upper guide 8 that accommodates a split die and the like.

[0003] On the other hand, a lower arm 10 is provided below the upper guide portion 8, and a distal end of the lower arm 10 is opposed to the upper guide portion 8 at a predetermined distance therefrom. A side guide section 12 is attached.
The workpiece 14 is fixed between the upper guide section 8 and the lower guide section 12. This lower arm 10,
The lower guide portion 12, the workpiece 14 and the like are accommodated in a processing tank (not shown).
It is made movable in the horizontal plane by the table. Then, the wire electrode W is stretched while being given a predetermined tension by a tension mechanism (not shown), and discharge machining is performed while feeding the wire electrode W in a predetermined direction, for example, downward by a wire electrode feeding mechanism and a wire electrode winding mechanism (not shown). Done. At this time, a machining fluid for electric discharge machining is generally used as a discharge medium, and a jet of the machining fluid is supplied to the wire electrode W from a machining fluid supply device (not shown). And
When electric discharge machining is performed while the wire electrode W and the workpiece 14 are relatively moved to form a tapered surface or the like, for example, the V-axis moving mechanism 4 or the U-axis moving mechanism 6 is appropriately moved so that the wire electrode is moved. W is inclined, and electric discharge machining is performed in this state.

In this type of wire electric discharge machine, as shown in FIG. 6, there is a structure between a wire electrode W to be fed and dies 11, 11 in guide portions 8, 12 of the electrode. Inevitably small, small, say 10
A clearance of about μm is inevitably generated, and therefore, the wire electrode is not completely supported by the wire guide portions 8 and 12, and the wire electrode W is slightly vibrated or fluttered during traveling.
That is, when a machining voltage is applied to the wire electrode W and the wire electrode W is brought close to the workpiece 14, a discharge occurs between them. In this case, the position where the discharge occurs is not specified. Processing starts with the energy of this discharge,
At the same time, the force generated at the time of the occurrence of the discharge gives the wire electrode W vibration. As described above, since the wire electrode W is not completely supported by the dies 11, 11,
The fulcrum of the vibration is not fixed. Therefore, the state of vibration cannot be specified.

This vibration is applied to the outer end surface 14 of the workpiece 14.
After the processing is started from a, the processing progresses for a while, and when the wire electrode W is completely cut into the workpiece 14, the wire electrode W is in a state of being sandwiched by the workpiece 14. Therefore, the above-mentioned vibration is suppressed to a small value, so that almost no problem occurs. However, at the beginning of the processing, the wire electrode W vibrates greatly as shown in FIG. Such vibration of the wire electrode W is not uniform because it is affected by various factors such as guide clearance, electrode diameter, tension, distance between upper and lower guides, and discharge generation position. Then, as the processing proceeds, the wire electrode W is cut into the inside of the workpiece 14, and when the processing proceeds to some extent, the workpiece 14 sandwiches the wire electrode W as described above. As a result, the vibration width of the wire electrode gradually converges, and when reaching a predetermined distance, the vibration becomes very small.

For this reason, for example, using a wire electrode having a diameter of 0.15 mm, for example, a material SKD having a thickness of 200 mm is used.
FIG. 7 shows a case where the workpiece made of −11 was subjected to electric discharge machining.
As shown also in the center cross-sectional view of the workpiece 14, the opening width L of the cutout on the outer end face of the workpiece 14 is L1 = 0.230 to 0.250 mm at 20 mm from the top, and L2 = 0 at the center. .345 to 0.355 mm, 20 from below
L3 = 0.325 to 0.250 mm at the point of mm, the central part is hollowed out to have a drum-like shape, and the error is remarkably large particularly at the central part of the workpiece, and the desired shape cannot be obtained. In addition, the edge 16 of the cut is rounded, and the depth L4 = about 0.4 mm and the width L5 = 0.0
There was a problem that sagging occurred over 525 mm.

[0007]

In the above situation, no problem arises when the end face portion is not directly related to the product shape, but when the end face portion is directly related to the product shape. However, when a high product accuracy is required, the machining cannot be completed only by the electric discharge machining as described above. Therefore, for example, FIG.
As shown in (b), a plurality of grooves 1 are formed on the end face of the workpiece 14.
9 is formed as a first processing method by cutting with a wire electrode W from an end surface 14c on a side different from the end surface 14b of the workpiece 14 in the processing progress direction, as shown in FIG. There is a processing method for processing into a desired shape 20 by processing in the direction of the arrow by a program. In this case, in the portion of the desired shape 20, the wire electrode W is dressed between workpieces, so that the vibration of the wire electrode W becomes small, and the sag hardly occurs.

However, in this processing method,
There has been a problem that extra processing time is required for cutting so as to be parallel to the end surface 14b in the processing progress direction. Further, in the corner portion shown at point D, apart from the vibration of the wire electrode W, there is a problem in the accuracy of the corner shape, for example, a problem in table feeding, a problem due to the influence of the fine vibration of the wire electrode, or a delay in the wire electrode. It was also necessary to consider the problem of sagging caused by the influence. Further, considering various circumstances as described above in advance, the NC
I had to write a program, which made machining very difficult. As a second processing method, FIG.
0, the wire electrode is connected to the outer end face 1 of the workpiece 14.
4b is cut while being stretched in a parallel state to form a groove portion 18 deeper than a desired depth, and then unnecessary portions 22 corresponding to an extra depth are removed by polishing or the like in another operation process. A method of completing a desired shape has been performed.

In this processing method, a portion in which sagging occurs due to the drum-shaped vibration of the wire electrode is deleted as an unnecessary portion 22, so that an appropriate shape can be obtained. In this case, however, an NC program must be used. At the time of preparation, it is necessary to correct only the dimensions to be polished and removed in advance, which is complicated. Furthermore, it was necessary to polish the polished surface so as to be parallel to the end surface 14b of the original shape, and therefore, the polishing operation required a skilled ability. In addition, such a polishing operation must be performed carefully, and there is a problem that it takes a very long time and the operation efficiency is extremely poor. The above-described problem occurs not only when electric discharge machining is started from the outer end surface 14a of the workpiece 14 but also when, for example, FIG.
As shown in FIG. 2B, a circular hollow 2 is formed in the workpiece 14.
4 and the inner end surface 1 that defines the hollow 24.
This also occurs when the groove 18 is formed radially from 4d. The present invention has been devised in view of the above problems and effectively solving them. SUMMARY OF THE INVENTION An object of the present invention is to provide a wire electric discharge machining method capable of preventing a wire electrode from vibrating or fluttering at the start of wire electric discharge machining.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a wire electrode which is stretched between an upper guide portion and a lower guide portion while feeding the wire electrode and a workpiece. In the wire electric discharge machining method in which electric discharge machining is performed by relatively moving the wire electrode, when performing electric discharge machining by cutting from an end face of the workpiece, before starting electric discharge machining, the wire electrode is inclined with respect to a machining progress direction. This was set at a predetermined angle with respect to the end face, the workpiece was subjected to electrical discharge machining for a predetermined distance in a state where the wire electrode was inclined, and then the inclination angle of the wire electrode was specified in advance. The electric discharge machining is performed while gradually changing to a designated angle, and when the inclination angle of the wire electrode reaches the designated angle, the electric discharge machining is performed along a preset shape.

[0011]

Since the present invention is constructed as described above, when the wire electrode is first cut into the workpiece, if the wire electrode is inclined, the wire electrode and the wire guide contact and are rubbed. The wire electrode is sent in this state. Then, the fluttering of the wire electrode caused by the clearance between the wire electrode and the wire guide portion is eliminated, and particularly, a portion having a small amplitude close to the upper guide portion or the lower guide portion becomes the discharge start point. That is, the vibration of the wire electrode is suppressed as if stopped by hand. As a result, the vibration or fluttering is rapidly converged, and the electric discharge machining is continued without causing almost any vibration in the cut portion of the workpiece. For this reason, the processed shape of the end face of the workpiece does not have a shape like a transfer of a drum-shaped vibration,
In addition, the end face edge portion is formed more sharply.

[0012]

Next, a wire electric discharge machining method according to the present invention will be described in detail with reference to the accompanying drawings. A wire electric discharge machine similar to that shown in FIG. 5 is used for carrying out the method of the present invention, and the present invention is implemented by rearranging the NC program according to the method of the present invention. Therefore, since the configuration of the wire electric discharge machine shown in FIG. 5 has been described above, the description thereof is omitted here. A first embodiment of the method of the present invention will be described in detail with reference to FIGS.
FIG. 1 is an explanatory view showing a state in which cutting is performed in a state where a wire electrode is inclined by advancing an upper guide portion in a traveling direction. FIG. 2 is a state in which drum-shaped vibration is suppressed at the time of starting cutting by a wire electrode. FIG. 3 is an explanatory diagram for explaining the method. The wire electrode W is sent out from the wire electrode feeding mechanism, passes through the upper guide section 8 and the lower guide section 12, and is wound by the wire electrode winding mechanism via the lower arm 10 (see FIG. 5). The movement of the workpiece 14 is performed by moving the X table and the Y table. The lower arm 10 is fixed to a column (not shown), and the lower arm 10 moves relative to the workpiece by moving the table. It is possible to do. The movement of the upper guide 8 in the horizontal plane is performed by the V-axis moving mechanism 4 provided on the machining head 2.
And by operating the U-axis moving mechanism 6.

Before starting the electric discharge machining, FIG.
As shown in FIG. 2A, the wire electrode W is inclined by advancing the upper guide portion 8 by an appropriate distance in the processing progress direction, and is inclined with respect to the outer end surface 14a of the workpiece 14 by θ.
Set the angle to. In the present embodiment, a case will be described in which the end face 14a at the start of processing is set to a substantially vertical state. The angle θ formed between the wire electrode and the end face is set so as not to be at least 0 °. In this state, as shown in FIG. 2A, the wire electrode to be fed vibrates largely with the upper and lower guides 8 and 12 as fulcrums. When the wire electrode W is inclined in this manner, the wire electrode W comes into contact with the wire guides 8, 12 to dies,
The wire electrode is sent while these are rubbed. Unlike the state in which the wire electrode is stretched in the vertical direction in this way, vibration or fluttering of the wire electrode W caused by the clearance between the wire electrode W and the wire guide or die is eliminated. When the wire electrode is tilted by a predetermined angle to eliminate vibration, the wire electrode and the workpiece 14 are then brought close to each other while maintaining the tilted state, and the upper end of the workpiece 14 is The cutting is started from the processing start point P of the edge portion.

When the machining is started by inclining the wire electrode W, as shown in FIG. 2B, a discharge is relatively easily generated at a point P where the gap is narrowed first. This portion is a portion having a relatively small amplitude, and makes it difficult to generate vibration due to the above-described operation. At this time, a minute vibration may be generated in the wire electrode W. When the wire electrode is cut into the workpiece, the wire electrode W is pressed by the cut groove, and the minute vibration converges. To go. That is, in this state, while maintaining the inclined state of the wire electrode W, a cut is further made by electric discharge machining as shown in FIG. 2C, and a predetermined cut is made as shown in FIG. Advance by distance S. The distance S is set, for example, to a distance until the lower edge of the workpiece 14 starts cutting by the wire electrode W2. That is,
When the cut is made by the distance S, the cut by the wire electrode is started over the entire thickness of the workpiece 14. Specifically, when the thickness of the workpiece 14 is 200 mm and the diameter of the electrode is 0.15 mm, the predetermined distance S is set to, for example, 0.4 mm. Therefore, the angle θ between the wire electrode and the outer end face 14a is tan θ = 0.4 /
200, for example, set to about 0.5 °. The value may be an experimental value stored in memory and automatically set. In this case, as the cutting proceeds, FIG.
As shown in FIG. 2 (c), the wire electrode is sandwiched by the workpiece 14 so that minute vibrations are further suppressed as if stopped by hand, and as shown in FIG. 2 (d). When the processed portion is formed over the entire thickness of the workpiece 14 by advancing by the distance S, the minute vibration rapidly converges, and the wire electrode cut into the workpiece is almost a drum-shaped vibration. Does not occur. Therefore, the opening shape of the processed portion on the outer end face of the workpiece 14 does not have a shape that transfers the drum-shaped vibration, and the end face edge portion is formed more sharply. In the illustrated example, the upper and lower guide portions 8 and 10 are far apart from the horizontal plane of the workpiece 14, but in reality, these guide sections 8 and 10 are extremely spaced from the horizontal plane of the workpiece 14. It is installed close to. Note that the inclination angle θ is an angle at which at least the wire electrode and the die of the guide portion can come into contact with each other.

[0015] After the incision is made by the predetermined distance S in this manner, the inclination angle of the wire electrode is gradually changed to the specified angle previously specified by the NC program while continuing the electric discharge machining. Go. In the illustrated example, the wire electrode W3 is substantially perpendicular to the horizontal plane, and the specified angle specified by the NC program is 0.
° is shown. In this manner, when the inclination angle of the wire electrode W3 reaches the angle specified by the NC program, the cutting by the electric discharge machining is further continued, and the electric discharge machining is performed according to a preset shape. In this embodiment, the outer end surface 14a of the workpiece 14 is substantially perpendicular to the horizontal plane, and the wire electrode W before the start of processing is also sent along the vertical direction. Is inclined by the angle θ to form an angle θ between the wire electrode and the outer end face. However, if the outer end face is inclined, the wire electrode is made to correspond to the inclination angle. Is set so as to maintain the above angle θ by changing the inclination angle of. For example, when the outer end surface 14a of the workpiece 14 is previously inclined at an angle θ with respect to the vertical, the cutting is started without inclining the wire electrode W at all, that is, at an inclination angle of 0 °. To

In the illustrated example, the case where the cutting is started from the outer end face 14a of the workpiece 14 has been described. However, the invention is not limited to this. For example, as shown in FIG. Inner end surface 14d that defines hole 24
The present invention can also be applied to the case where the cut is started from. In addition, even when the wire electrode is gradually returned at the time when the workpiece is cut to the center, the effect of reducing the shape droop can be obtained. Further, the cut distance for maintaining the inclination angle of the wire electrode is set so that at least the processed part of the wire electrode is cut into the workpiece by at least half or more, and desirably, the entire wire is cut.

Next, a second embodiment of the method of the present invention will be described with reference to FIG. In the first embodiment, the wire electrode is inclined by slightly moving the upper guide portion in the processing direction. However, in the second embodiment, the lower guide portion is moved in the processing direction. The wire electrode is inclined by slightly moving the wire electrode to advance. That is, first, in the wire electrode that is being sent along a substantially vertical direction, the lower guide portion is slightly moved relative to the traveling direction to advance, and the wire electrode is inclined at a predetermined angle in the traveling direction. Let it. Then, the wire electrode W5 is advanced while maintaining this inclined state, and the cutting is started from the processing start point C by the wire electrode near the lower guide portion. After starting the cutting in this way, until the wire electrode near the upper guide portion starts processing the workpiece 14,
While maintaining the wire electrode W6 in the inclined state at the predetermined angle, the cutting process is performed for a predetermined distance S.

In this manner, when the machining is started over the entire thickness of the workpiece 14, the inclination angle of the wire electrode W7 is changed to the angle designated by the NC program while the cutting by the electric discharge machining is continued. Change gradually. Then, when the inclination angle of the wire electrode W8 reaches the angle specified by the NC program, thereafter, the wire electrode W9 is advanced along the shape specified by the NC program to continuously perform electric discharge machining.

Next, a third embodiment of the method of the present invention will be described with reference to FIG. In the first and second embodiments described above, the case where the processing surface of the workpiece is formed in the vertical state has been described. In the present embodiment, the case where the cut surface has a taper is described. Will be described. As shown in FIG. 4, first, the wire electrode W is inclined by a predetermined angle with respect to the traveling direction by slightly advancing the upper guide portion 8 relatively along the traveling direction. In parallel with this operation or after this operation is completed, in order to form a tapered surface specified in the NC program, the wire electrode W
Is inclined by an angle α corresponding to the angle of the tapered surface in a plane orthogonal to the traveling direction. The wire electrode W10 thus inclined is advanced to reach the machining start point C. Then, after starting the notch processing, the wire electrode near the lower guide portion 10 is connected to the workpiece 1.
Until the machining of No. 4 is started, electric discharge machining is performed while maintaining the wire electrode W11 in the inclined state at the predetermined angle.

When the wire electrode in the vicinity of the lower guide portion 10 starts to be cut by a predetermined distance and starts machining, the inclination of the wire electrode in the wire advancing direction is gradually reduced while continuing the electric discharge machining. Finally, the inclination angle in the traveling direction is set to 0 °. In this case, in order to form the tapered surface, the inclination is maintained only at the same angle as the angle of the tapered surface in a plane perpendicular to the wire electrode traveling direction. Then, while maintaining the inclined state, the wire electrode W12 is cut by electric discharge machining along the shape set in the NC program. As described above, in the present invention, at the beginning of electric discharge machining, a slight inclination angle is provided between the wire electrode and the end face of the workpiece with respect to the traveling direction of the wire electrode. Processing is performed so that the end surface comes into contact at one point, and then the cutting is performed gradually. Therefore, the wire electrode and the guide portion come into contact with each other, so that the wire electrode does not flutter, vibration generated in the wire electrode is suppressed, and the processing opening can be prevented from becoming excessively large.

As is clear from the comparison between the first and second embodiments, this action is similarly obtained when cutting from the wire electrode near the upper guide portion and when cutting from the wire electrode near the lower guide portion. Be demonstrated. In addition, when the wire electrode is inclined in the processing direction, as long as the wire electrode reaches a predetermined inclination angle before the electric discharge is started between the wire electrode and the workpiece, the table, that is, the workpiece, is inclined. It may be performed while moving the workpiece relatively, or
The wire electrode W may be tilted at a predetermined angle from the beginning, or the wire electrode W may be tilted at a predetermined angle while relatively moving the table. In addition, it goes without saying that the above-described functions and effects are exhibited irrespective of the thickness and the material of the workpiece. Further, the apparatus for carrying out the method of the present invention is not limited to a wire electric discharge machine as shown in FIG. 5 as long as it can perform taper processing.

As a result of performing the method of the first embodiment under the condition that the diameter of the wire electrode is 0.15 mm and the thickness of the workpiece is 200 mm, the opening width L of the notch as shown in FIG. L1 = 0.230-0.2 at 20mm from above
5 mm, L2 = 0.245-0.265 m at the center
m, L3 = 0.235-0.25 at 20 mm from below
5 mm, as compared with the conventional method,
It was found that the opening width was extremely small, and that the method of the present invention exhibited an excellent vibration suppressing effect. Before starting the machining, sag (see FIG. 7) of the shape when the wire electrode is inclined with respect to the machining surface by 0 ° to 12 ° as shown in Table 1 in advance in the machining progress direction is measured. confirmed.

[0023]

[Table 1]

As is clear from Table 1, the dimension L4 hardly changes with respect to the inclination angle of the wire electrode. However, when the inclination angle is increased from 0, the dimension L5 of the sag gradually decreases, and the inclination angle becomes 0. The effect is seen at about 0.5 °, and the size L5 of the sag is considerably reduced. In particular, the inclination angle is 1 ° to 12 °.
In the range of °, the dimension L5 of the sag is greatly reduced, and although there is a slight variation, it is constant at about 5 μm, showing a good effect. In addition, the inclination angle of the wire electrode is 12 °.
It is considered that the same effect can be obtained even if the value is larger than the above, if judged from the above results. As described above, in the vertically suspended state of the wire and the state in which the wire electrode is slightly inclined as in the method of the present invention, the processing accuracy is improved when the wire electrode is slightly inclined as in the present invention. Was completed. This was clearly recognizable in appearance. If the angle of inclination is too large, it becomes difficult to apply the jet flow or the shape of the next machining program is affected. Therefore, it is preferable to incline the angle so that such a problem does not occur.

[0025]

As described above, according to the present invention,
The following excellent functions and effects can be achieved. Vibration of the wire electrode itself at the start of wire electric discharge machining can be suppressed. Therefore, the opening width of the processing portion at the processing end surface can be suppressed to a necessary minimum to prevent the width from being excessively widened, and also it is possible to prevent the generation of sagging at the processing portion, thereby greatly improving the processing accuracy. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a state in which a cutting is performed in a state where a wire electrode is inclined by advancing an upper guide portion in a traveling direction.

FIG. 2 is an explanatory diagram for explaining a state in which vibration is suppressed at the start of cutting by a wire electrode.

FIG. 3 is an explanatory diagram showing a state in which a cutting is performed in a state where a wire electrode is inclined by advancing a lower guide portion in a traveling direction.

FIG. 4 is an explanatory view showing a state in which the method of the present invention is applied when forming a tapered surface.

FIG. 5 is a schematic configuration diagram showing a wire electric discharge machine.

FIG. 6 is a diagram showing a relationship between a wire electrode and a die of a guide unit.

FIG. 7 is a view showing the occurrence of sagging during processing of a wire electrode.

FIG. 8 is an explanatory diagram showing a specific example of a processing shape.

FIG. 9 is an explanatory diagram for explaining a processing method that has been conventionally employed for preventing sagging on a processing end surface.

FIG. 10 is an explanatory diagram for explaining another processing method that has been conventionally employed for preventing sagging on a processing end surface.

FIG. 11 is an explanatory view showing another specific example of a processing shape.

[Description of Signs] 2 Processing head 4 V-axis moving mechanism 6 U-axis moving mechanism 8 Upper guide section 10 Lower arm 12 Lower guide section 14 Workpiece 14a Outer end face 14b Inner end face P, C Processing start point S Distance W Wire Electrode θ Predetermined angle

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-121829 (JP, A) JP-A-63-127829 (JP, A) JP-B-57-49335 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) B23H ^7/ 02-7/30

Claims (1)

(57) [Claims] 1. A wire electric discharge machining method for performing electric discharge machining by moving a wire electrode stretched between an upper guide portion and a lower guide portion while relatively moving the wire electrode and a workpiece. When performing electric discharge machining by cutting from the end face of the workpiece, before starting electric discharge machining, the wire electrode is inclined with respect to a machining progress direction and set at a predetermined angle with respect to the end face, and the wire In the state where the electrode is inclined, the workpiece is subjected to electrical discharge machining for a predetermined distance, and thereafter, the electrical discharge machining is performed while gradually changing the inclination angle of the wire electrode to a designated angle designated in advance, and the electrical discharge machining is performed. When the inclination angle reaches the specified angle, the electric discharge machining is performed along a preset shape.