JP2015083334A - Wire electric discharge machine automatically correcting machining route according to corner angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire electric discharge machine correcting a machining route according to an angle between two moving blocks forming a corner portion.SOLUTION: The wire electric discharge machine includes: reading and analyzing blocks of a machining program 20 from a machining program storage unit 21; when a corner angle detecting unit 22 determines that a corner is present, computing a correction distance and a return distance on the basis of the corner angle detected by the corner angle detecting unit 22; implementing the correction so that an end point of a block to be machined first is extended according to the correction distance; removing a portion from a start point of a block to be machined subsequently to an intermediate point of this block according to the return distance; creating a machining route by a machining route correcting unit 23 so that the end point of the new block created by the extension is connected to the start point of the other new block created by the removal; and moving a wire electrode 3 along the machining route relative to a workpiece 2 by a machining route control unit 24.

Description

  The present invention relates to a wire electric discharge machine, and more particularly, to a wire electric discharge machine that automatically corrects a machining path in accordance with a corner angle.

  In wire electrical discharge machining, the wire electrode moves in a direction different from the machining progress direction (opposite direction or direction at a certain angle) due to the electric discharge repulsive force generated between the wire electrode and the workpiece or the turbulent flow of the machining fluid. It is known to bend. When processing linearly with a wire electrode, the wire electrode bends in the direction opposite to the processing progress direction, but does not affect the processing shape. However, in the processing of the corner portion, the influence of bending appears greatly, and the shape accuracy of the corner portion is greatly reduced, so-called “corner dripping” occurs, and the intended shape cannot be obtained.

  FIG. 1 is a schematic diagram for explaining that a corner portion is processed by a wire electrode 3 of a wire electric discharge machine. In wire electric discharge machining, in order to machine the workpiece 2 to a desired dimension, an offset path is created by adding the radius of the wire electrode 3 and the discharge gap to the actual product shape dimension. In general, the wire electrode 3 is moved along the offset path. The offset path is referred to as a machining path 4. A value obtained by adding the radius of the wire electrode 3 and the discharge gap is referred to as an offset value.

  As shown in FIG. 1, the wire electrode 3 does not move along the machining path 4 due to bending at the corner portion of the workpiece 2, but moves inside the machining path 4 (see the wire electrode locus 5 indicated by a broken line). Then, the workpiece 2 is excessively processed. Therefore, a so-called “corner droop” (see the corner droop 6 resulting from the bending of the wire electrode) is formed, and a desired finished shape cannot be obtained. Various countermeasures have been proposed to deal with such problems. If various countermeasures are roughly divided, they can be roughly divided into two types of countermeasures.

<Countermeasure 1> A method of reducing the bending of the wire electrode by suppressing the machining speed and the amount of the machining liquid at the corner and extending the discharge pause time (so-called “energy control”).
<Countermeasure 2> Method of correcting machining path in consideration of bending of wire electrode FIG. 2 shows the above-described countermeasure for correcting the machining path in order to avoid excessive machining of the workpiece due to bending of the wire electrode. It is a figure explaining the measure 2. FIG.
When the machining path 4 of the wire electrode 3 is corrected by the correction path 7 and the wire electric discharge machining is performed, the wire electrode 3 moves as indicated by the wire electrode locus 8. Thereby, it can avoid that the to-be-processed object 2 is processed excessively.

  Among the countermeasures 1 and 2, the method of correcting the machining path of the countermeasure 2 has an advantage that the machining time by the wire electric discharge machine is shorter than the method of controlling the energy of the countermeasure 1 so far. Several correction methods have been proposed. Among several proposals for correction methods, a technique for paying attention to the deflection amount of the wire electrode and correcting the machining path based on the deflection amount is disclosed in, for example, the following documents.

Patent Document 1 discloses a control unit that controls the relative movement amount of a wire electrode, a storage unit that stores the amount of bending of the wire electrode on the workpiece processing surface, and a calculation unit that sequentially determines the processing direction of the wire electrode by calculation. And the control apparatus of the wire electric discharge machine provided with the drive part which drives a wire electrode with the correction amount equal to the bending amount of a wire electrode is disclosed.
In Patent Document 2, the bending amount of the wire electrode being processed in wire-cut electric discharge machining is stored for each processing condition, and based on this bending amount, the wire electrode is allowed to escape excessively in the advancing direction during punching. A sharp edge machining method is disclosed in which a machining path is corrected so as to make a notch during die machining.

Patent Document 3 discloses a control unit that controls a relative movement amount of a wire electrode, a corner detection unit that detects a corner part in a machining path, and a tangential movement of a predetermined distance and a predetermined distance of the detected corner part. A wire electric discharge machining apparatus including a machining path correction unit that sequentially performs correction of movement and asymptotic return movement is disclosed.
In Patent Document 4, the first machining path is extended tangentially at the corner in the machining progress direction, and the second and third correction paths are set at an angle larger than the angle of the machining corner. A method of correcting a machining path so as to return to the original machining path by the path and a wire electric discharge machining apparatus for realizing this are disclosed.

Japanese Patent Laid-Open No. 61-219529 Japanese Patent Laid-Open No. 7-285029 Japanese Unexamined Patent Publication No. 7-24645 JP-A-11-207527

  The techniques disclosed in Patent Document 1 and Patent Document 2 are techniques for correcting the machining path by using the deflection amount of the wire electrode as a correction amount. However, these correction methods focus on machining when the corner angle is 90 degrees. The other corner angles are not discussed in detail. It is widely known that when the corner angle is reduced (<90 degrees), the wire electrode is more affected by disturbances such as the flow of machining fluid at the corner apex, and the machining accuracy of the corner is further deteriorated. Therefore, there is a problem that a desired machining shape cannot always be obtained if correction is performed with the same correction amount for all corner angles regardless of the corner angle.

  The techniques disclosed in Patent Document 3 and Patent Document 4 each correct the machining path in three steps or more, change a part of the correction amount according to the corner angle, and determine other correction amounts based on experimental values. This is a technique for determining the correction amount depending on the technique and either the machining type or the thickness of the workpiece according to the corner angle. Since the techniques disclosed in these patent documents all correct the machining path by a number of steps, a plurality of correction amounts are necessary.

  In the technique disclosed in Patent Document 3, a part of the correction amount is determined according to the corner angle, but there is a description or suggestion as to how the correction amount is specifically changed according to the corner angle. It has not been. In addition, it takes a lot of time and trouble to find various setting values that can be used for various machining patterns that exist in the world that are required by the user. There is a very difficult problem to decide.

  In the technique disclosed in Patent Document 4, four correction amounts are determined by either the processing type or the plate thickness of the workpiece according to the corner angle. Even with the same processing type, the degree of bending of the wire electrode differs depending on the material of the workpiece, the plate thickness, and the like. If correction is performed with the same correction amount, the desired shape accuracy cannot always be obtained. For the same reason, there is a problem that even if the plate thickness of the workpiece is the same, if the processing type or the material of the workpiece is different, the desired shape accuracy cannot be obtained unless the correction amount is adjusted. Further, this Patent Document 4 does not show how to specifically change the correction amount according to the corner angle.

  Accordingly, an object of the present invention is to provide a wire capable of correcting the machining path in accordance with the angle formed by the two moving blocks forming the corner portion and improving the shape accuracy at the time of machining in view of the above-described problems of the prior art. It is to provide an electric discharge machine.

  The invention according to claim 1 of the present application creates a machining path on the basis of an axis movement command of a machining program, and performs machining first in a corner portion formed by two continuous movement blocks in the created machining path. Correct the end point of the block to be extended, delete the block to be processed next from the start point to the middle of the block, and process the next block with the new block end point created by extending the previously processed block A wire electric discharge machine for performing machining by correcting a machining path so as to connect a new block start point created by deleting a part of the block, and a corner angle obtaining unit for obtaining a corner angle of the corner part And a machining path correction unit that corrects the machining path according to the corner angle, and the machining path correction unit extends an end point of the block to be processed first. The distance that extends the end point when correcting in this way is the correction distance a, and the distance between the block start point before the deletion of the block to be processed next and the new block start point created by deletion is the return distance b. The wire electric discharge machine corrects the machining path of the corner portion so that one or both of the correction distance a and the return distance b becomes smaller as the corner angle becomes larger.

The invention according to claim 2
The machining path correction means includes
The correction distance a and the return distance b are
a = P
b = Q / tan (θ / 2) + R
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by obtaining a constant related to a wire electrode diameter.

The invention according to claim 3
The machining path correction means includes
The correction distance a and the return distance b are
a = Q / tan (θ / 2)
b = P
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: The wire electric discharge machine according to claim 1, wherein the machining path is corrected based on an offset amount.

The invention according to claim 4
The machining path correction means includes
The correction distance a and the return distance b are
a = b * sin α / sin (θ−α)
b = P
Where α = tan ⁻¹ {P / (Q + R)}
θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by obtaining a constant related to a wire electrode diameter.

The invention according to claim 5
The machining path correction means includes
The correction distance a and the return distance b are
a = P / sin θ
b = Q / tan (θ / 2) + R
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by obtaining a constant related to a wire electrode diameter.

The invention according to claim 6
The correction distance a and the return distance b are
a = b * sin α / sin (θ−α)
b = Q / tan (θ / 2) + R
Where α = tan ⁻¹ {P / (Q + R)}
θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by obtaining a constant related to a wire electrode diameter.

  According to a seventh aspect of the present invention, instead of the amount of bending of the wire electrode, a constant determined for each electrical processing condition, the offset amount includes a radius value of the wire electrode, a radius value of the wire electrode, and a discharge gap value. The wire electric discharge machine according to any one of claims 2 to 6, wherein the wire electric discharge machine is any one of an added value or a constant determined for each electrical machining condition.

  According to the present invention, it is possible to provide a wire electric discharge machine capable of correcting a machining path in accordance with an angle formed by two moving blocks forming a corner portion and improving shape accuracy during machining.

It is a mimetic diagram explaining processing a corner part with a wire electrode of a wire electric discharge machine. It is a figure explaining the method of correct | amending a process path | route, in order to avoid that a workpiece is processed excessively by the bending of a wire electrode. It is a figure explaining the correction method of the processing course in the present invention (when the angle of a corner part is 90 degrees). It is a figure explaining the correction | amendment method of the process path | route in this invention (when the angle of a corner part is smaller than 90 degree | times). It is a figure explaining that a wire electrode vibrates or bends in a process advancing direction when a wire electrode is pinched | interposed into the process groove | channel of a to-be-processed object. It is a figure explaining that a wire electrode bends in the processed groove | channel when a wire electrode exists in the intersection of the two process grooves of a to-be-processed object. It is a block diagram explaining the structure of the principal part of the wire electric discharge machine which concerns on this invention. It is a figure explaining the method of Embodiment 1 which correct | amends the process path | route by making the distance which extends the end point of the block processed previously into the fixed correction distance a. It is a figure explaining the method of performing the correction | amendment of a process path | route, making the distance which deletes the block to process next from the start point to the middle of a block the return distance b. It is a figure explaining the case where the correction distance a is made constant and the return distance b is changed according to the corner angle. It is a flowchart explaining the process performed in the process path | route correction | amendment part in embodiment of this invention. It is a figure explaining Embodiment 1 which calculates | requires the correction | amendment path | route when fixing the correction distance a and changing the return distance b according to a corner angle. It is a figure explaining Embodiment 2 which calculates | requires the correction | amendment path | route when fixing the return distance b and changing the correction distance a according to a corner angle. 6 is a diagram illustrating a correction path in the case of the first embodiment. FIG. It is a figure explaining the correction | amendment path | route in the case of Embodiment 2. FIG. It is a graph explaining that the correction amount changes so that the correction distance decreases as the corner angle increases, and the correction distance increases as the corner angle decreases. It is a figure explaining Embodiment 3 (when corner angle (theta) is 90 degree | times). It is a figure explaining Embodiment 3 (when corner angle (theta) is smaller than 90 degree | times). It is a figure explaining that both the correction distance a and the return distance b change according to a corner angle. It is a figure explaining the other example which calculates | requires the position of the intersection of a correction | amendment path | route. It is a figure explaining Embodiment 4 (when corner angle (theta) is 90 degree | times). It is a figure explaining Embodiment 4 (when corner angle (theta) is smaller than 90 degree | times). It is a figure which expands and demonstrates FIG. It is a figure explaining the relationship that both the correction distance a and the return distance b become small when a corner angle becomes large. It is a figure explaining the relationship between the correction | amendment distance a and the return distance b, and the angle (alpha). It is a figure explaining the method of calculating | requiring the position of the intersection of a correction | amendment path | route. It is a figure explaining return distance b of Embodiment 1, Embodiment 3, and Embodiment 4. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The wire electric discharge machine of the present invention corrects the end point of the block to be processed first to be extended at the corner portion formed by two continuous moving blocks in the processing path, and then starts the block to be processed next from the start point. Various correction amounts are prepared in wire electrical discharge machining that corrects the machining path so as to connect the new block end point created by deleting and extending the block and the new block start point created by deletion. Therefore, the machining path is corrected so as to improve the shape accuracy of the corner portion even when machining is performed at a corner angle other than 90 degrees.

  Therefore, the present invention creates a correction path according to the corner angle in order to improve the lack of shape accuracy by correcting the machining path with the amount of deflection of the wire electrode. Specifically, the present invention corrects the machining path of the corner portion so that the correction amount increases as the corner angle decreases, and the correction amount decreases as the corner angle increases.

  Here, the reason why the machining path is corrected as described above in order to improve the machining shape accuracy in wire electric discharge machining will be described with reference to FIGS. The workpiece 2 is processed by the wire electrode 3, and processed grooves having the processed groove wall 15 and the processed groove wall 16 as both walls are processed. 3 and 4, the intersections of the perpendicular and the machining path 9 drawn from the vertex C of the corner of the workpiece 2 to the machining path 9 indicated by the alternate long and short dash line are B and D, respectively, and the machining path before correction Is the intersection of A.

  As shown in FIG. 3, when the corner angle θ of the corner portion is 90 degrees, the area formed by the square ABCD is Sa. On the other hand, as shown in FIG. 4, when the corner angle θ of the corner portion is smaller than 90 degrees, the area formed by the square ABCD is Sb. When the discharge gap is the same, the square area Sb (see FIG. 4) constituted by the points A, B, C, and D having the corner angle θ (<90 degrees) is the area Sa (FIG. 3) in the case of the 90-degree corner. See).

  FIG. 5 is a diagram for explaining that the wire electrode 3 vibrates or bends in the machining progress direction when the wire electrode 3 is sandwiched between the machining grooves 11 of the workpiece 2. FIG. 6 is a diagram for explaining that the wire electrode 3 bends in the processed groove when the wire electrode 3 exists at the intersection of the two processing grooves 11 and 12 of the workpiece 2.

  As shown in FIG. 5, when the wire electrode 3 is sandwiched between the machining grooves 11 of the workpiece 2, the wire electrode 3 vibrates 17 or bends in the machining progress direction 13 and deviates from the wire electrode position 14 on the program. However, when the wire electrode 3 exists at the intersection of the two processing grooves 11 and 12 as shown in FIG. 6, the wire electrode 3 does not simply vibrate 17 or bend in the processing progress direction 13. There is a tendency to flow (bend) in the processed groove due to the influence of the flow of the machining liquid supplied into the machining grooves 11 and 12 (see flow (deflection) 18). When the wire electrode 3 enters the processed groove, it is sandwiched between the processed grooves and there is no adverse effect on the processed shape.

  The “play” space that can be formed at the corner apex is defined by the area of the above-described square ABCD (see FIGS. 3 and 4). Therefore, the larger the area of the quadrilateral ABCD, the easier it is for the wire electrode 3 to flow in the direction of the previously processed groove (flexibility), and the shape accuracy of the corner apex deteriorates.

  As shown in FIG. 4, the area Sb of the square ABCD when the corner angle θ (<90 degrees) is larger than the area Sa of the square ABCD when the corner angle θ shown in FIG. 3 is 90 degrees. In other words, the “play” space is large. For this reason, when creating a correction path for the machining path, this "play" space must be taken into account, and the correction amount must be larger than when the corner angle is 90 degrees. For the same reason, when the corner angle θ is larger than 90 degrees, the “play” space becomes smaller, and the correction amount must be smaller than the correction amount when the corner angle is 90 degrees.

  For the reasons described above, the present invention provides a corner angle θ in order to improve the processing accuracy of the corner portion reliably when machining the corner portion of a workpiece having various corner angles θ using wire electric discharge machining. As the angle becomes smaller, the correction amount becomes larger, and when the corner angle θ becomes larger, the machining path of the corner portion is corrected so that the correction amount becomes smaller.

Here, a method for reducing the labor of changing the correction amount according to the corner angle θ will be described.
As described above, the greatest cause of the corner droop (see FIG. 1) is the bending of the wire electrode 3. Therefore, if the bending amount of the wire electrode 3 is used as a parameter for calculating a correction amount for correcting the machining path, the bending amount of the wire electrode 3 can be efficiently obtained regardless of the corner angle θ. A correction path can be created. Then, the machining path is corrected to extend the end point of the block to be processed first, the next block to be processed is deleted from the start point to the middle of the block, and the new block end point created by extension is deleted. The correction distance and the return distance may be used in order to perform correction so as to connect the new block start point created in this way, and it is possible to save the trouble of considering various correction amounts.

Next, the structure of the principal part of the wire electric discharge machine according to the present invention will be described.
FIG. 7 is a block diagram illustrating a configuration of a main part of the wire electric discharge machine according to the present invention. The wire electric discharge machine according to the present invention can automatically correct the machining path in accordance with the angle formed by the two moving blocks forming the corner portion. A machining program block is read from the machining program storage unit 21 in which the machining program 20 is stored and analyzed, and the corner angle detection unit 22 determines whether there is a corner. When there is a corner, a correction path is created in the machining path correction unit 23 according to the angle, and the wire electrode 3 is moved relative to the workpiece 2 by the machining path control unit 24. When there is no corner, the machining path control unit 24 moves the wire electrode 3 relative to the workpiece without creating a correction path.

  The machining path correction unit 23 calculates a correction distance and a return distance based on the corner angle detected by the corner angle detection unit 22, and corrects the end point of the block to be processed earlier according to the correction distance, The next block to be processed is deleted from the start point to the middle of the block according to the return distance, and the processing path is corrected so that the new block end point created by extension and the new block start point created by deletion are connected. Then, the corrected machining path is output to the machining path control unit 24.

  Next, each embodiment of the present invention will be described. As described above, in the prior art, a method of creating a correction path using the deflection amount of the wire electrode as a correction amount has been proposed, but the method of returning to the original machining path is not specifically shown. It was. Therefore, each embodiment of the present invention considers a method of returning to the original machining path, and creates a correction path according to the corner angle θ.

<Embodiment 1>
(When the correction distance a is fixed to the bending amount of the wire electrode and the return distance b is changed according to the corner angle θ to obtain the correction path)
As shown in FIG. 8, the distance for extending the end point of the block to be processed first is a correction distance a, and the distance for deleting the next block to be processed from the start point to the middle of the block is a return distance b. The correction distance a is defined as a wire electrode deflection amount v. The portion 2 a of the workpiece 2 is processed by the wire electrode 3. If the wire electrode 3 enters the machining groove, the wire electrode 3 is bent in the direction opposite to the machining progress direction by being sandwiched by the groove, but is hardly bent in the other direction.

  Therefore, as shown in FIG. 9, a perpendicular is drawn from the corner apex 32 of the workpiece 2 to the machining path 30, and the intersection is defined as an intersection 33. The distance from the corner vertex 32 to the intersection 33 is the offset amount (offset). The corner vertex 32 means the corner vertex of the shape after machining the workpiece 2.

  The distance between the corner vertex 34 and the intersection 33 on the machining path is defined as the return distance b of the wire electrode 3. A corner apex 34 on the machining path is an intersection of a block to be machined before the machining path is corrected and a block to be machined next. That is, it is the end point of the block to be processed first and the start point of the block to be processed next. In order to obtain the correction distance a and the return distance b, an arithmetic expression such as Equation 1 can be considered.

  It can be seen from Equation 1 that the return distance b changes according to the corner angle θ. When the corner angle θ increases up to 120 degrees, the return distance b decreases, and when the corner angle θ decreases, the correction amount changes so that the return distance b increases (see FIG. 10). In this way, the correction method for changing the return distance b in accordance with the corner angle θ does not depend on the corner angle θ. Shape accuracy can be improved. The corner angle θ can be calculated using the inner product of the block to be processed first and the block to be processed next.

  In the above description, the case where the correction distance a is constant and the return distance b is changed according to the corner angle θ has been described as an example. However, the return distance b is constant and the correction distance a is changed according to the corner angle θ. Thus, the shape accuracy of the corner portion can be improved (see FIG. 16). Moreover, it is also possible to add a constant to the equation for obtaining the return distance b depending on the machining conditions and required accuracy. Further, in the present embodiment, the return distance b is calculated using a trigonometric function using an offset value, but it is also conceivable to obtain the return distance b using other parameters and calculation methods.

FIG. 11 is a flowchart for explaining processing executed by the machining path correction unit in the embodiment of the present invention. Hereinafter, it demonstrates according to each step.
[Step ST01] The correction distance a is determined based on the deflection amount v of the wire electrode.
[Step ST02] The corner angle θ is read.
[Step ST03] The return distance b is calculated based on the corner angle θ.
[Step ST04] The return distance b is output.
[Step ST05] A correction path is commanded, and the process ends.

<Embodiment 2>
(When the return distance b is fixed to the bending amount of the wire electrode, and the correction distance a is changed according to the corner angle θ to obtain the correction path)
In the first embodiment, the machining path correction method in which the deflection amount v of the wire electrode 3 is set as the correction distance a and the return distance b is changed according to the corner angle θ is described as an example regardless of the corner angle θ. FIG. 12 is a diagram illustrating Embodiment 1 in which a correction path is obtained when the correction distance a is fixed and the return distance b is changed according to the corner angle. The first embodiment clearly shows that the correction method for changing the return distance b according to the corner angle θ has a higher shape accuracy of the corner portion than the case where both the correction distance a and the return distance b are corrected by the deflection amount of the wire electrode 3. Became. Accordingly, it is conceivable to improve the shape accuracy of the corner portion by fixing the return distance b and changing the correction distance a according to the corner angle.

  In the second embodiment, a correction method in which the return distance b is fixed and the correction distance a is changed according to the corner angle will be described as an example. FIG. 13 is a diagram illustrating Embodiment 2 in which a correction path is obtained when the return distance b is fixed and the correction distance a is changed according to the corner angle.

  As described above, when the wire electrode 3 enters the machining groove, bending occurs in the direction opposite to the machining progress direction, but there is almost no bending in the other direction (see FIG. 5). Therefore, if the processing of the block to be processed first is finished, the corner portion is folded back, and the wire electrode 3 enters the processing groove of the block to be processed next, it is considered that there is no influence on the shape accuracy of the corner portion.

  Therefore, as described in the first embodiment, in the case of the machining progress direction shown in FIG. 14 (in the case of the first embodiment) and FIG. 15 (in the case of the second embodiment), the intersection point of the machining path before correction by the corner angle θ. If the wire electrode 3 moves from A to a point B that is off offset / tan (θ / 2), the adverse effect on the corner apex due to the bending of the wire electrode 3 is eliminated.

  For the same reason, it can be seen that if the wire electrode 3 moves from the intersection A to the point D that is offset / tan (θ / 2), the adverse effect on the corner shape starts. Therefore, in FIG. 12, the area of the square ABCD is a “play” space of the wire electrode 3 that affects the shape of the corner portion.

  As in the first embodiment, when the corner angle θ is 90 degrees, the shape accuracy of the corner portion can be improved if the correction distance a is the amount of deflection of the wire electrode 3 and the return distance b is an offset value. it can. That is, in order to correct the “play” space due to the area of the quadrilateral ABCD, the correction may be made with the area of the triangle AEB having the correction distance a and the return distance b on both sides (FIG. 12 (Embodiment 1)).

Therefore, if the area relationship between the rectangle ABCD in FIG. 14 (square A ₁ B ₁ C ₁ D ₁ in FIG. 15) and the triangle AEB (triangle A ₁ E ₁ G ₁ ) is used, the return distance b is fixed and corrected. A correction path when the distance a is changed according to the corner angle θ can be obtained (see FIGS. 12 and 13).

When the corner angle θ and the offset value are the same, the area of the square ABCD in FIG. 14 is equal to the square A ₁ B ₁ C ₁ D ₁ in FIG. 15 (see FIGS. 14 and 15). Therefore, in order to correct the “play” space of the quadrangle A ₁ B ₁ C ₁ D ₁ in FIG. 15, correction is performed with the area of the triangle A ₁ E ₁ G ₁ in FIG. 15 having an area equal to the triangle AEB in FIG. do it.

  In FIG. 14, the area of the triangle AEB can be obtained by Equation 2.

In FIG. 15, the area of the triangle A ₁ E ₁ G ₁ is obtained by Equation 3.

When the area of the triangle A ₁ E ₁ G ₁ in FIG. 15 is equal to the area of the triangle AEB in FIG. 14, the “play” space by the square A ₁ B ₁ C ₁ D ₁ in FIG. Then, the correction distance a can be obtained by the equation (4).

  As described above, the correction distance a and the return distance b can be obtained by Equation 5.

  From Equation 5, it can be seen that the correction distance a changes according to the corner angle θ. When the corner angle θ increases up to 120 degrees, the correction distance a decreases, and when the corner angle θ decreases, the correction amount changes so that the correction distance a increases (see FIG. 16). In this way, the correction method of fixing the return distance b and changing the correction distance a according to the corner angle θ corrects both the correction distance a and the return distance b with the deflection amount v of the wire electrode regardless of the corner angle θ. The shape accuracy of the corner portion can be improved as compared with the case of performing the above.

<Embodiment 3>
(When the correction distance a and the return distance b are changed in accordance with the corner angle θ to obtain a correction path)
The first embodiment is a method of correcting the machining path by changing the bending amount v of the wire electrode to the correction distance a and changing the return distance b according to the corner angle regardless of the corner angle θ. The second embodiment is a method of correcting the machining path by changing the wire electrode deflection amount v to the return distance b regardless of the corner angle θ and changing the correction distance a according to the corner angle.

  In the correction method for changing the return distance b or the correction distance a according to the corner angle θ, the shape accuracy of the corner portion is higher than when the correction distance a and the return distance b of the prior art are corrected by the deflection amount v of the wire electrode. This has been clarified by the first and second embodiments. Therefore, it is conceivable that the shape accuracy can be further improved by changing both the correction distance a and the return distance b in accordance with the corner angle.

Therefore, in the third embodiment, a correction method in which both the correction distance a and the return distance b are changed according to the corner angle will be described with reference to FIGS. As described in the second embodiment, the points separated from offset / tan (θ / 2) on the two machining paths forming the corner from the corner apex A (A1) on the machining path are respectively point B (B ₁ ) and Let it be point D (D ₁ ). The area of the square ABCD composed of corner vertex A, point B, point C and point D on the machining path in FIG. 17 and corner vertex A ₁ , point B ₁ , point C ₁ and point D on the machining path in FIG. The area of the quadrangle A ₁ B ₁ C ₁ D ₁ constituted by ₁ is the “play” space where the wire electrode is at the corner of the corner.

In the case of the first embodiment, when the corner angle θ is 90 degrees, the shape accuracy of the corner portion can be improved by setting the correction distance a as the deflection amount v of the wire electrode and the return distance b as the offset value. it can. That is, when the corner angle θ is 90 degrees, in order to avoid the “play” space formed at the apex, it is necessary to perform correction with the area of the triangle AEB having both the correction distance a and the return distance b (see FIG. 17). Therefore, for the same reason, if the area of the triangle A ₁ E ₁ B ₁ for avoiding the quadrangle A ₁ B ₁ C ₁ D ₁ formed at the corner vertex of FIG. The shape accuracy of the corner portion can be improved.

In order to obtain the area of the triangle A ₁ E ₁ B _1, a rectangle ABCD shown in FIG. 17 where the corner angle θ can be a vertex of 90 degrees and a rectangle A shown in FIG. 18 where the corner angle θ can be a corner vertex of an arbitrary angle. The area relationship of ₁ B ₁ C ₁ D ₁ may be used.

In FIG. 18, the area S1 of the quadrangle A ₁ B ₁ C ₁ D ₁ that can be a corner having an arbitrary corner angle θ is obtained as follows.
In triangle A ₁ G ₁ F ₁ and triangle F ₁ D ₁ C ₁ ,
∠G ₁ A ₁ F ₁ = ∠D ₁ F ₁ C ₁
∠A ₁ G ₁ F ₁ = ∠F ₁ D ₁ C ₁
G ₁ F ₁ = D ₁ C ₁ = offset
Because there is a relationship
ΔA ₁ G ₁ F ₁ ≡ΔF ₁ D ₁ C ₁
It can be seen that it is.
Accordingly, the area S1 of the quadrangle A ₁ B ₁ C ₁ D ₁ is obtained by the equation (6).

  The area S of the quadrilateral ABCD formed when the corner angle θ is 90 degrees can be obtained by Expression 7.

  Therefore, the ratio of the “play” area that can be formed at the corner apex of the corner angle θ and the “play” area when the corner angle θ is 90 degrees is expressed by the following equation (8).

Therefore, if the area relationship between the triangles A ₁ E ₁ B ₁ (see FIG. 18) and AEB (see FIG. 17) for correcting the “play” space is expressed by Equation 8, even if the corner angle θ is an acute angle, the corner The shape accuracy of the corner portion can be improved such that the angle is 90 degrees. Further, since the area of the triangle AEB when the corner angle θ is 90 degrees (see FIG. 17) is (v * offset) / 2, the area S2 of the triangle A1E1B1 when the corner angle θ is an arbitrary angle in FIG. It is calculated like the formula.

  Therefore, the correction distance a for correcting the corner portion where the corner angle θ is an arbitrary angle can be obtained by the area relation of the triangle and the trigonometric function.

  As described above, the correction distance a and the return distance b can be obtained by Expression 11.

  As can be seen from Equation 11, both the correction distance a and the return distance b change according to the corner angle (see FIG. 19). When the corner angle θ decreases between 120 degrees, both the correction distance a and the return distance b increase, and when the corner angle θ increases, both the correction distance a and the return distance b decrease. As described above, the correction method for changing the correction distance a and the return distance b in accordance with the corner angle θ has higher shape accuracy than the correction method for fixing both the correction distance and the return distance of the prior art.

In the third embodiment, the position of the intersection E (E1) of the correction path is obtained using the polygonal area and the trigonometric function as described above. However, as shown in FIG. 20, the machining path AB (A _{1) is obtained.} if B ₁₎ machining path in parallel to AB (a ₁ B ₁₎ from the wire electrode 3 deflection amount v (= h) only and the workpiece 2 a straight line away on the opposite side EH and (E ₁ H ₁₎ There is also a method of obtaining E (E ₁ ) as the intersection of the straight line EH (E ₁ H ₁ ) and the straight line obtained by extending the machining path CA (C ₁ A ₁ ).

<Embodiment 4>
In the third embodiment, the shape accuracy of the corner portion can be improved by changing both the correction distance a and the return distance b in accordance with the corner angle θ. The correction method of the third embodiment can improve the shape accuracy of the corner portion as compared with the correction method in which both the correction distance a and the return distance b of the prior art are fixed to the deflection amount v of the wire electrode. Here, as the fourth embodiment, another example of a correction method for changing both the correction distance a and the return distance b in accordance with the corner angle θ will be described.

  As described in the first and third embodiments, if the wire electrode 3 reaches the line segment BC, the wire electrode 3 may be sandwiched by the processing groove and bend in the direction opposite to the processing progress direction. Therefore, the shape of the corner portion is not adversely affected. For this reason, the formula b = offset / tan (θ / 2) may be used to obtain the return distance b.

  In the first embodiment, when the corner angle θ is 90 degrees, if the correction distance a is the deflection amount v of the wire electrode and the return distance b is offset / tan (θ / 2), high shape accuracy can be obtained at the corner portion. I explained that. That is, B is a point that is offset / tan (θ / 2) in the horizontal direction (X-axis direction) from the block intersection A before correction, and B is the deflection amount v of the wire electrode in the vertical direction (Y-axis direction). If the point is E, the defect of the corner portion can be corrected by returning the wire electrode 3 to the machining path along the line EB that forms an angle α with the machining path AB (FIG. 21). Therefore, as shown in FIG. 22, even when the corner angle θ is an arbitrary angle, it is considered that the shape accuracy of the corner portion can be improved by returning the same angle to the machining path. As shown in FIG. 21, the angle α (= ∠ABE) can be obtained by Expression 12.

The return distance b and the angle α can be calculated as described above, and the correction distance a can be obtained using the relationship of triangles. A method for obtaining the correction distance a will be described with reference to FIG. FIG. 23 is an enlarged view of the triangle A ₁ E ₁ B ₁ of FIG.

In the triangle A ₁ E ₁ B ₁ , there is a relationship expressed by the following equation (13).

  Since there is a relationship of Equation 13, the correction distance a can be obtained by Equation 14.

  For this reason, the correction distance a and the return distance b can be calculated by Equation 15.

  As can be seen from equation (15), it can be seen that both the correction distance a and the return distance b change according to the corner angle θ. Further, when the corner angle θ decreases between 120 degrees, both the correction distance a and the return distance b increase, and when the corner angle θ increases, both the correction distance a and the return distance b decrease. Yes (see FIG. 24). By such a correction method, a shape accuracy much higher than that of the correction method in which both the correction distance a and the return distance b of the prior art are fixed can be obtained.

In the present embodiment, the angle α between the position of the intersection E (E ₁ ) of the correction path and the return path EB (E ₁ B ₁ ) and the machining path AB (A ₁ B ₁ ) to be processed later is constant as described above. However, it can also be obtained as shown in FIG. That is, if the point that is offset / tan (θ / 2) from the machining path intersection A before correction is B and the point that returns from the machining path by an offset from point B is F, the length of the wire from point F is bent. There is also a method of drawing an amount perpendicular line FG in the opposite direction to the workpiece, extending a straight line connecting point B and point G in the BG direction, and having the intersection point with the machining path to be machined first as E. is there.

  Furthermore, a method is also conceivable in which the return distance b is set to a constant and the correction distance a is obtained by the equation 14 to correct the machining path. In this case as well, higher shape accuracy can be obtained than in the prior art method in which both the correction distance and the return distance are fixed to the bending amount of the wire electrode.

  Here, the return distance b of the first embodiment, the third embodiment, and the fourth embodiment will be additionally described. In each embodiment, the return distance b is determined by a mechanism in which the correction path returns to the original machining path at point B (intersection where a perpendicular is drawn from the corner vertex to the machining path). However, with this method, when machining with a strong machining fluid, such as when processing high-speed machining or thick plates, the wire electrode is placed in the machining groove of the block that has already been machined by the powerful machining fluid flow. There is a concern that it will be washed away and the shape of the corner apex will be deteriorated.

  Therefore, in such a case, it is effective to increase the return distance b until it is not affected by the machining groove. Specifically, as shown in FIG. 27, the radius of the wire electrode 3 is defined as a position where the wire electrode completely passes through the point B, that is, a position advanced from the point B by about 0.5 to 1.5 wire diameters. It returns to the original machining path at a position determined by a numerical value such as the value, diameter value, wire electrode deflection amount v, wire radius, and diameter, and the extension is an arbitrary constant R as shown in Equation 16 The return distance b may be determined. Hereinafter, the arbitrary constant R is referred to as a constant related to the wire electrode diameter.

  Here, using the constant R, the correction distance a can be obtained by the same concept as in each embodiment.

  Here, a method for obtaining the correction distance a based on the same concept as in the fourth embodiment will be described. The correction distance a and the return distance b can be calculated by Equation 17.

  The relationship between the correction distance a and the return distance b and the angle α is as shown in FIG.

Next, in order to help understanding of each embodiment of the present invention, common points of the first to fourth embodiments will be described.
In the first to fourth embodiments, when the corner angle θ decreases, either or both of the correction distance a and the return distance b increase, and when the corner angle θ increases, either one or both of the correction distance a and the return distance b decreases. Thus, the shape accuracy of the corner portion is improved. In any case, higher shape accuracy than the prior art can be obtained. In the first to fourth embodiments, a right angle and an acute angle have been described as examples. However, an obtuse angle can also be applied.

  In Embodiments 1 to 4, a new block end point created by extending the end point of the block to be processed first, and a new block start point created by deleting from the start point of the block to be processed next to the middle of the block, However, in order to connect these two points, it may not be a straight line such as an arc.

  In the first to fourth embodiments, even if the wire electrode deflection amount v used for obtaining the correction distance a and the return distance b is a value obtained through experiments, the electrical working conditions, the strength of the working fluid, and the wire diameter It may be a theoretical constant that is obtained dynamically from the thickness of the material.

  In the first to fourth embodiments, the offset amount (offset) is used to obtain the correction distance a and the return distance b. Instead, the wire radius value corresponding to the offset amount, the wire radius and the discharge gap are set. An added constant or a constant determined for each electrical processing condition may be used.

When these are applied to the formulas of the respective embodiments, they can be expressed as follows.
(Embodiment 1)
a = P
b = Q / tan (θ / 2) + R
However, P is the amount of bending of the wire electrode, Q is the amount of offset, and R is a constant related to the diameter of the wire electrode.
(Embodiment 2)
a = Q / tan (θ / 2) + R
b = P
However, P is the amount of bending of the wire electrode, Q is the amount of offset, and R is a constant related to the diameter of the wire electrode.
(Embodiment 3)
a = P / sin θ
b = Q / tan (θ / 2) + R
However, P is the amount of bending of the wire electrode, Q is the amount of offset, and R is a constant related to the diameter of the wire electrode.
(Embodiment 4)
a = b * sin α / sin (θ−α) where α = tan ⁻¹ {P / (Q + R)}
b = Q / tan (θ / 2) + R
However, P is the amount of bending of the wire electrode, Q is the amount of offset, and R is a constant related to the diameter of the wire electrode.

Next, differences between the first embodiment, the second embodiment, the third embodiment, and the third embodiment will be described.
The first embodiment is a correction method for improving the shape accuracy of the corner portion by fixing the correction distance a and changing only the return distance b according to the corner angle. Although the prior art has clearly discussed the correction path, it has not been specifically shown how the wire electrode returns to the original processing path after correction. The first embodiment describes a method for solving this problem and returning the corrected wire electrode to the original path.

  The second embodiment is a correction method for improving the shape accuracy of the corner portion by fixing the return distance b and changing only the correction distance a according to the corner angle. It is the same that the distance for correcting the machining path is fixed on one side and the other side is changed according to the corner angle, but the one to be changed (fixed) is different. In order to crush the loophole of the present application, the rights are considered.

  On the other hand, in the third embodiment, both the correction distance a and the return distance b are changed according to the corner angle θ to improve the shape accuracy of the corner portion. As shown in Embodiment 1 (Embodiment 2), by changing the return distance b (correction distance a) according to the corner angle θ, the shape accuracy is higher than the conventional method of fixing both the correction distance and the return distance. Became clear.

  Therefore, it is considered that high shape accuracy can be obtained by changing not only the return distance b (correction distance a) but also the correction distance a (return distance b) according to the corner angle. The third embodiment describes a correction method for obtaining a desired shape by changing both correction amounts according to the corner angle. In the fourth embodiment, the correction distance a and the return distance b are both changed according to the corner angle to improve the shape of the corner portion. The method of obtaining the correction distance a is different from that of the third embodiment, and the correction distance a is obtained so that the correction distance a forms a certain angle with the return path of the wire electrode and the original processing path to be processed later, and the processing path is corrected. Is. By such a correction method, higher shape accuracy than the prior art can be obtained.

DESCRIPTION OF SYMBOLS 2 Workpiece 3 Wire electrode 4 Processing path 5 Wire electrode locus 6 Corner droop resulting from bending of wire electrode 7 Correction path 8 Wire electrode locus 9 Processing path 10 Actual position due to bending of wire electrode 11 Processing groove 12 Processing groove 13 Processing Traveling direction 14 Wire electrode position on program 15 Machining groove wall 16 Machining groove wall 17 Vibration 18 Flow (deflection)

20 machining program 21 machining program storage unit 22 corner angle detection unit 23 machining path correction unit 24 machining path control unit

30 Machining path 31 Correction path 32 Corner vertex 33 Intersection 34 Corner vertex on machining path 35 Wire electrode (command position)
36 Wire electrode (actual position)

a Correction distance b Return distance θ Corner angle v Wire electrode deflection amount offset Offset amount P Wire electrode deflection amount Q Offset amount R Constant for wire electrode diameter

Claims (7)

Creates a machining path based on the axis movement command of the machining program, and corrects to extend the end point of the block to be machined first at the corner formed by two consecutive moving blocks in the created machining path The next block to be processed is deleted from the start point to the middle of the block, and the new block end point created by extending the block to be processed first and the middle of the block to be processed next are deleted and created. A wire electric discharge machine that performs machining by correcting the machining path so as to connect the new block start point,
Corner angle obtaining means for obtaining a corner angle of the corner portion;
Machining path correction means for correcting the machining path according to the corner angle,
The machining path correction means sets the distance for extending the end point when correcting so as to extend the end point of the block to be processed first as a correction distance a,
The return distance b is the distance between the block start point before the deletion of the block to be processed next and the new block start point created by deletion.
A wire electric discharge machine that corrects a machining path of the corner portion so that one or both of the correction distance a and the return distance b becomes smaller as the corner angle becomes larger. The machining path correction means includes
The correction distance a and the return distance b are
a = P
b = Q / tan (θ / 2) + R
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by a constant relating to a wire electrode diameter. The machining path correction means includes
The correction distance a and the return distance b are
a = Q / tan (θ / 2)
b = P
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: The wire electric discharge machine according to claim 1, wherein the machining path is corrected based on an offset amount. The machining path correction means includes
The correction distance a and the return distance b are
a = b * sin α / sin (θ−α)
b = P
Where α = tan ⁻¹ {P / (Q + R)}
θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by a constant relating to a wire electrode diameter. The machining path correction means includes
The correction distance a and the return distance b are
a = P / sin θ
b = Q / tan (θ / 2) + R
Where θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by a constant relating to a wire electrode diameter. The correction distance a and the return distance b are
a = b * sin α / sin (θ−α)
b = Q / tan (θ / 2) + R
Where α = tan ⁻¹ {P / (Q + R)}
θ: Corner angle
P: Deflection amount of wire electrode
Q: Offset amount
The wire electric discharge machine according to claim 1, wherein R: the machining path is corrected by a constant relating to a wire electrode diameter.   Instead of the deflection amount of the wire electrode, a constant determined for each electrical processing condition, the offset amount is a value obtained by adding the radius value of the wire electrode, the radius value of the wire electrode and the value of the discharge gap, or electrical The wire electric discharge machine according to claim 2, wherein the wire electric discharge machine is one of constants determined for each machining condition.

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