JPH04217426A - Wire electric discharge maching method and device thereof - Google Patents

Abstract

PURPOSE:To machine a circular section in wire electric discharge machining with high precise and efficiency. CONSTITUTION:In wire discharge machining containing finishing following roughing, a reference radius is preset, the radius of a circular section of a machining shape is compared with the reference radius during roughing, and the circular section is machined after transformed into a corner shape formed by two lines or machined in a machining process which is put in contact with a longitudinal machining process for inserting therein a smaller circular arc than a preset radius, if the radius of the circular section is below the reference radius. The circular section is restrained from sagging during roughing and finished precisely and efficiently.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electrical discharge machining method and an apparatus therefor, which can machine a circular arc portion within a machined shape in a short time while improving machining accuracy.

0002

2. Description of the Related Art FIG. 15 is a configuration diagram showing a conventional wire electrical discharge machining apparatus. In the figure, 1 is a wire electrode, 2 is a workpiece, and 3 is a wire electrode 1 and a workpiece 2, which are provided facing each other. A machining fluid supply device that supplies machining fluid 4 to a machining gap formed between them; 5 is a machining power supply that applies a pulse voltage between the wire electrode 1 and the workpiece 2; 6 is a machining portion of the workpiece 2; 7
is an X-Y cross table on which the workpiece 2 is placed, 8a is an X-axis servo motor for freely moving the X-Y cross table 7 in the X-axis direction, and 8b is an X-Y cross table 7
Y-axis servo motor to move freely in the Y-axis direction,
9 is a servo unit that controls the drive of the X-axis servo motor 8a and the Y-axis servo motor 8b, and 10 is a numerical control device that outputs control information on the movement amount and movement speed of the X-Y cross table 7 to the servo unit 9. .

Next, the operation will be explained. As is well known, wire electrical discharge machining uses a wire electrical discharge machining apparatus as shown in FIG. A machining fluid 4 is supplied from a machining fluid supply device 3 to the machining gap, and a machining power source 5 is connected between the wire electrode 1 and the workpiece 2.
The X-Y cross table 7 on which the workpiece 2 is placed is moved via the X-axis and Y-axis servo motors 8a and 8b while applying a pulse voltage to repeatedly generate a continuous electric discharge in the machining gap. By moving, the processing portion 6 is moved arbitrarily and the workpiece 2 is processed into a predetermined contour shape. The movement amount and movement speed of the X-Y cross table 7 are determined by movement information sent from the numerical control device 10 to the servo unit 9, and based on the control information, the servo unit 9 controls the X-axis and Y-axis servo motors 8a, 8b. is controlled, and a predetermined contour shape is processed.

Now, for example, as shown in FIG. 16, when the wire electrode 1 is advanced along the path A→C→E to machine the corner of the workpiece 2, the outer corner portion 11a and the inner corner portion 11b are , it is known that "sagging" as shown by the solid line occurs. The reason for this is that the wire electrode 1 is a non-rigid body. That is, due to the repulsive force of the discharge generated between the wire electrode 1 and the workpiece 2,
Since the wire electrode 1 is bent and the actual movement of the wire electrode 1 is along the path A→B→D→E, the outer corner portion 11a is redundantly processed, and the inner corner portion 11b is processed redundantly. This is because machining remains. Further, the size of this "sag" increases as the repulsive force of the discharge increases, that is, as the machining speed increases, and in normal rough machining, it becomes about several tens of micrometers to several hundred micrometers.

Also, for the same reason, a minute arc corner as shown in FIG.
→ E, the actual movement of the wire electrode 1 is along the path A → B → G → D → E, so the outer corner part 11a and the inner corner part 11b are similar to the above.
``Who'' will be born in . The size of this "drop" increases as the radius of the arc becomes smaller, and when the radius of the arc increases to a certain extent, the size of the "drop" becomes smaller. Due to the above-mentioned tendency, these "drops" become a problem especially in the case of edge corners formed from two straight lines, a straight line and a circular arc, or a minute circular arc corner.

Now, the corners machined by wire electrical discharge machining include sharp edge corners shown in FIG. 16 and circular arc corners shown in FIG. In most cases, when machining corner parts, a minute arc (hereinafter referred to as corner R: usually R=0.
1mm to 0.3mm) is inserted for processing.

Therefore, it is necessary to improve the "sloping" of the corner R, but in wire electrical discharge machining, in order to improve machining accuracy, the machining conditions are changed using the same path information after performing what is commonly called rough machining. A second cut machining method is used in which finishing machining is performed by changing only the path correction value (also called offset), and according to this machining method, the corner shape accuracy of the workpiece 2 can be improved. is known to be possible. The reason for this is that the machining allowance in the second cut machining that is performed following rough machining as finishing machining is minute (usually about 5 μm to 10 μm).
Therefore, the repulsive force generated by the discharge is much smaller than that during rough machining, and as a result, the deflection of the wire electrode 1 is also reduced accordingly, so that "sagging" at the corner part during finishing machining is much smaller than that during rough machining. This is because it is always smaller than that during machining, and it is possible to gradually correct the "sag" at the corner.

Normally, in order to automatically perform second cut processing, the processing speed, processing conditions, path correction, subprogram call, etc. are described in the main program, and this subprogram contains the wire information from the processing start point to the processing end point. A command for relative movement between the electrode 1 and the workpiece 2 is written, and predetermined processing is executed according to this main program. As an example of such a machining method, a second cut machining method that automatically performs rough machining (first cut machining) to finishing machining (second cut machining) according to program instructions is disclosed in Japanese Patent Application Laid-Open No. 102724/1982. ing.

[0009]

[Problems to be Solved by the Invention] Since the conventional wire electric discharge machining method is performed as described above, the size L1 of the "sag" after rough machining is determined by the machining during finishing machining, as shown in FIG. If the difference in offset between rough machining and finishing machining is smaller than the size L1 of this "drop", the out corner part 11a will be machined as a "drop" during rough machining. It becomes impossible to correct the damaged portion, and as a result, machining accuracy decreases.

In addition, in order to avoid this problem and finish the out corner portion 11a into a corner shape without "sag", the amount of offset during rough machining is adjusted to the size of "sag" L1.
Therefore, the amount of machining or the number of machining operations during finishing machining must be increased, and the total machining time also increases accordingly, resulting in a decrease in machining efficiency. Furthermore, when finishing the inner corner portion 11b after rough machining, the "sag" during rough machining must be removed, which increases the amount of machining and requires finishing using weaker machining conditions than rough machining. During machining, if the amount removed at the inside corner portion 11b increases, the machining tends to become unstable, resulting in a decrease in machining accuracy.In addition, as described above, the finishing machining causes " If a large offset amount is used to correct the droop, the total machining time during finishing machining will further increase, as described above.
There was a problem that processing efficiency was reduced.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an electric discharge machining method and an apparatus therefor that can machine arcuate parts with high precision and efficiency.

0012

[Means for Solving the Problems] The first invention is a wire electrical discharge machining method in which rough machining is followed by finishing machining to machine a workpiece into a predetermined shape, in which a reference radius is set in advance, If the result of determining whether or not it is rough machining is rough machining, the radius of the circular arc part within the machining shape is compared with the above reference radius, and if the radius of the circular arc part is less than the reference radius, the above circular arc part is It is processed by converting it into a corner shape formed by a straight line.

[0013] The second invention is a wire electric discharge machining method in which rough machining is followed by finish machining to machine a workpiece into a predetermined shape, and the radius of the circular arc portion within the machining shape is equal to or less than a preset reference radius. For the circular arc part, in the first machining, the circular arc part is machined using a machining path formed by inserting an arc that is in contact with the machining path before and after this circular arc part and has a smaller radius than a predetermined radius, and then inserted in the subsequent machining. The radius of the inserted circular arc is gradually made larger than the radius of the previously inserted circular arc, and the machining path is changed while machining is performed.

[0014] The third invention is to convert the arc smaller than the predetermined radius of the second invention into a desired shape in the next machining based on the outer diameter of the wire electrode used, the current machining gap, and the next machining gap. It is the smallest circular arc that can be modified in shape.

[0015] A fourth aspect of the present invention is a wire electrical discharge machining apparatus that performs finishing machining following rough machining to machine a workpiece into a predetermined shape, and a discriminating means for determining whether or not rough machining is being performed;
A comparison processing unit that compares the radius of the circular arc part in the machining shape with a preset reference radius, and when the above respective results are rough machining and the radius of the circular arc part is less than the reference radius, the circular arc part is divided into two straight lines. and an arithmetic processing means comprising a conversion processing section that converts the corner shape into a corner shape formed by.

[0016] The fifth invention is a wire electric discharge machining apparatus that performs finishing machining after rough machining to machine a workpiece into a predetermined shape, and includes a determining means for determining the number of times of machining, and a determining means for determining the number of times of machining, and When the results of the comparison section that compares the radius with a preset reference radius, the discrimination means, and the comparison section are a predetermined number of machining operations and the radius of the arc portion is less than or equal to the reference radius,
The apparatus is equipped with an arithmetic processing means comprising a conversion processing section that converts the circular arc portion into a machining path formed by inserting a circular arc that is in contact with the machining path before and after the circular arc portion and has a radius of a predetermined radius or less.

[0017]

[Operation] In the first invention, in the stage of rough machining performed prior to finishing machining, if the radius of the circular arc part in the machining shape is equal to or less than a preset reference radius, the circular arc part is cut by two straight lines. The corner shape is converted into the shape of the corner to be formed, and the "sagging" of the circular arc portion during rough machining is suppressed.

[0018] In the second invention, if the radius of the circular arc part within the machining shape is equal to or less than a preset reference radius, the circular arc part is brought into contact with straight lines before and after the circular arc part in the first machining, and Insert an arc smaller than a predetermined radius, change the machining shape, and then gradually increase the radius of the inserted arc while changing the machining path and process to eliminate the "slop" in the arc part. suppress.

[0019] In the third invention, the circular arc inserted in the first time in the second invention is determined as desired in the next machining based on the outer diameter of the wire electrode used and the machining gap during the current machining and the next machining. The shape is set to the minimum arc that can be corrected to suppress "sloping".

In the fourth invention, the determining means determines whether or not rough machining is being performed, and the arithmetic processing means compares the radius of the circular arc portion within the machining shape with a preset reference radius, and each If the result of the above means is rough machining and the radius of the circular arc part is less than the reference radius, the circular arc part is converted into a corner shape formed by two straight lines, and the "sloping" of the circular arc part during rough machining is suppress.

[0021] In the fifth invention, if the results of the comparison section of the discriminating means and the arithmetic processing means are that the predetermined number of machinings is a predetermined number of times and the radius of the arc part is less than or equal to the reference radius, the conversion processing section of the arithmetic processing means Then, the above circular arc part is processed by converting it into a machining path formed by inserting a circular arc that touches the machining path before and after this circular arc part and has a radius less than a predetermined radius, and gradually changes the radius of the inserted arc in subsequent machining. Processing is performed while increasing the size to suppress the "sagging" of the circular arc portion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a numerical control device for realizing an embodiment of the first and fourth inventions. In the figure, 101 is a program memory that stores various programs, 102 is an NC tape, 103 is a tape reader that reads the contents of the NC tape 102, and 104 is an arithmetic processing means that stores the arc radius of the corner shape and a predetermined value. and a conversion processing section that converts the corner shape into a corner shape formed by two straight lines, and an arithmetic processing section that executes various arithmetic processing; 105 is a coordinate value used for route calculation; 106 is a variable memory that stores data that corresponds to a discriminating means and has a switch function to execute various controls depending on the contents; 107 is a calculation processing unit 104;
A pulse distributor 108 executes a pulse distribution calculation based on the movement amounts Δx, Δy in the X direction and Y direction, and generates distributed pulses Px and Py in the X and Y axes, and 108 is external to the device. 9a is an X-axis servo unit that drives the X-axis servo motor 8a based on the distribution pulse Px, and 9b is a Y-axis servo that drives the Y-axis servo motor 8b based on the distribution pulse Py. It is a unit.

Next, the operation will be explained. The main operations of the process when a given processed shape is subjected to second cut processing (including third cut processing) are as shown in the flowchart of FIG. That is, when machining is started as shown in step S1, it is determined in step S2 whether or not the machining target locus is a corner part, and if the determination result is not a corner part, the process moves to step S3, Machining is performed using normal path correction. This normal path correction means, as shown in Fig. 10, that the machining path is corrected by offsetting the final shape by the sum of the wire diameter and the machining gap, and at the arc corners, the concentric circles of the program shape The route is corrected by

If the result of this determination is that it is a corner, the process moves to step S4 and the radius r of the arc of the corner is determined.
is calculated. Subsequently, in step S5, it is determined whether the machining currently being performed is rough machining, and if the determination result is not rough machining, the process moves to step S3. If the determination result is rough machining, the process moves to step S6, where the radius r of the circular arc calculated in step S4 is compared with a reference radius R that is preset as a predetermined value,
If the radius r of the circular arc is larger than the reference radius R, the process moves to step S3. The reference radius R is, for example, set in a range that is greater than or equal to the wire diameter and less than or equal to 1.0 mm. If the radius r of the circular arc is less than or equal to the reference radius R, the process proceeds to step S7, and the corner portion having the radius r of the circular arc is formed into a corner shape formed by straight lines that touch the circular arc at the starting point and the ending point of the circular arc. Convert and process. The above operations are repeated until the program end, and when the program end is confirmed as shown in step S8, the machining is completed.

Next, using the NC program shown in FIG.
The above process will be explained in more detail by taking as an example a case where a shape as shown in FIG. 4 is processed. In FIG. 3, (1) is the main program whose program name is indicated by L1000, (2), (4), and (6) are variables whose program name is indicated by H100 and are substituted with the number of machining operations, and (3), (5). , (7) indicate the NC data of first cut processing, second cut processing, and third cut processing, respectively, character string F is processing speed, E is processing condition, H1 is a variable to which path correction value is substituted,
G22 is an instruction code for calling a subprogram. (8) is a subprogram whose program name is L2000, (9) is an instruction code for M80 to supply the machining fluid 4, M82 to feed the wire electrode 1, and M84 to turn on the machining power source 5, (10) ), G01 moves in a straight line,
The instruction code for G02 to command arc movement, (1
1) is an instruction code in which M85 instructs to turn off the machining power supply 5, M83 instructs to finish feeding the wire electrode 1, and M81 instructs to cut off the supply of machining fluid 4. (12) is represented by G23 and returns to the main program L1000. This is an instruction code that commands.

Now, in order to process the shape shown in FIG. 4 by second cutting, first, the main program L1000 and the subprogram L
2000 and stores the program memory 101.
Store in. Subsequently, when execution of the main program L1000 is instructed via the operation panel 108, the arithmetic processing unit 1
04 executes program discrimination based on the program name, and based on the program data, the main program L1
Start processing 000. Next, as shown in (2),
Since the content of the variable H100 is set to "1" indicating the first machining, the machining in this case is determined to be the first cut machining. Next, the machining speed and machining conditions set by the character strings F and E are set in a1 and b1, and the variable H for the corner conversion processing switch is set.
1 is substituted with the route correction value c1.

Subsequently, when the instruction code G22 is determined by the arithmetic processing unit 104, the subsequent subprogram L
2000 reads are performed. Subprogram L2
When 000 is read out, instruction codes M80, M82, and M84 are determined, and the machining fluid 4 is supplied and the wire electrode 1 is
At the same time, the feeding of the wire electrode 1 and the workpiece 2 is started.
A pulse voltage is applied in between, and relative movement between the wire electrode 1 and the workpiece 2 is started according to the next movement command, and electrical discharge machining is executed. That is, first, the instruction code G92
When it is determined, (X0, Y0) is written into the machining start point area (Xs, Ys) of the work memory 105. Next, the instruction code G01 is determined, and △x1 and △y1 are the linear movement amount areas (△xa, △ya) of the working memory 105.
and is simultaneously input to the pulse distributor 107. The pulse distributor 107 has a linear movement amount area (△xa,
Execute pulse distribution calculation based on the contents of △ya) and
Axis and Y-axis distribution pulses are input to the X-axis servo unit 9a and the Y-axis servo unit 9b, respectively. These X-axis servo unit 9a and Y-axis servo unit 9b drive the X-axis servo motor 8a and the Y-axis servo motor 8b.
is driven, and this driving force causes the X-Y cross table 7 to
moves, and the path P0→P1 shown in FIG. 4 is processed.

[0028] Since the next line is also the instruction code G01,
Processing similar to the above is performed to process the path P1→P2. Then, at the time when the next instruction code G02 is determined, it is determined whether the content of the variable H100 for the corner conversion processing switch in the variable memory 106 is "1". As a result, in this case, the content of the variable H100 for the corner conversion processing switch is "1", so first,
The arc movement area of the working memory 105 (△Xb, △Yb
, Δi, Δj), the data following the instruction code G02 is stored, and furthermore, the data following the instruction code G01 in the next line is stored in (Xc, Yc) of the working memory 105. and,
The radius r of the arc is calculated from Δi and Δj stored in the arc movement amount area (ΔXb, ΔYb, Δi, Δj), and the result is written in the radius data area of the work memory 105.

[0029]

[Formula 1]

[0030] Then, in advance, the variable H1 in the variable memory 106 is
The reference radius R set to 01 is compared with the calculated radius r of the circular arc, and if the result is r≦R, the following corner processing is performed. That is, at present, the machining start point area (Xs, Ys
) is the coordinate value of point P1, that is, (X0+△x1, Y0+
△y1) is stored, and the linear movement amount area (△
(xa, △ya) stores (△x2, △y2).

[0031] Then, the linear movement amount area (△xa, △ya) and the circular movement amount area (△Xb, △Xb,
Based on the values stored in △Yb, △i, △j), (Xc, Yc) and the machining start point area (Xs, Ys), the intersection point ( Xp, Yp) can be obtained from the following formula.

[0032]

[Formula 2]

[0033] From this equation 2, x and y are determined and set as the intersection point (Xp, Yp) of the above two straight lines. Then, based on these values, the contents of the machining start point area (Xs, Ys) are changed to (Xs+△
x2, Ys+△y2) as the coordinate value of the machining start point of point P2, and also set the linear movement amount area (△Xa, △Ya
) to (Xp-Xs, Yp-Ys) to perform linear machining as the linear movement amount, and further set the contents of the machining start point area (Xs, Ys) to (Xp, Yp) and the linear movement amount area. The contents of (△Xa, △Ya) are (Xe-Xp, Ye-
By setting Yp) and performing machining from the intersection point (Xp, Yp) to point P4, the corner part is converted to a corner shape formed by two straight lines, and machining is performed along the converted corner shape. Implemented.

[0034] Thereafter, the machining continues in the same way while performing the above-mentioned processing, but here, for example, in the circular arcs P4 and P5, the circular movement amount areas (△Xb, △Y
If the radius r of the arc calculated from the values of △i5 and △j5 stored in Even if there is, corner processing is not executed and normal arc movement processing is executed.

When the processing of the machining path information shown in (10) of FIG. , the feeding of the wire electrode 1 is commanded, and the feeding of the machining fluid 4 is commanded to stop the machining. Then, as shown in (12), when the command code G23 is determined, the process returns to the main program L1000. Thereafter, following the completion of the first cut process, a second cut process is started according to the main program L1000. In this machining, as shown in (4) of the main program L1000, it is determined that the content of the variable H100 for the corner conversion process switch in the variable memory 106 is "2", that is, it is other than first cut machining. Therefore, in the subsequent process, the process of converting the corner portion into a corner shape formed by two straight lines as described above is not executed, and machining is performed based on the machining path by normal correction. After this second cut process is completed, a third cut process is subsequently started. In this machining as well, the main program L1
As shown in (6) of 000, the content of the variable H100 for the corner conversion processing switch in the variable memory 106 is “3”.
”, that is, it is determined that the process is other than the first cut process, so the same process as the second cut process is executed.

As described above, in first cut machining, which is rough machining, corners with a radius less than the reference radius R are converted into a corner shape formed by two straight lines sandwiching the corner portion, and a shape corresponding to the corner shape is converted. After performing the above-mentioned processing, the corner portion can be processed into a desired shape by performing predetermined finishing processing. Therefore, as shown in FIG. 6, even if the corner portion has a large "sag" during rough machining, the desired corner portion can be finished without a large offset difference during rough machining. Further, when creating route information for finishing machining, there is no need to perform special corner processing, so there is no need to create separate programs for rough machining and finishing machining.

FIG. 7 is a block diagram of a numerical control device for realizing an embodiment of the second, third, and fifth inventions. The same reference numerals as in FIG. 1 indicate the same parts, and the explanation will be omitted. Reference numeral 104a denotes an arithmetic processing means, which includes a comparison section that compares the arc radius of the corner shape with a predetermined value, a conversion processing section that converts the machining path of the corner portion from the machining gap corresponding to the machining conditions, and also performs various calculations. The arithmetic processing unit 109 that executes the process is a machining condition memory that stores the electrical condition parameters of the machining power source and the machining gap etc. when machining is performed under the electrical conditions.

Next, the operation will be explained. The main operations of the process when performing second cut processing (including multiple cuts beyond third cut processing) on a given processing shape are as follows:
This is as shown in the flowchart of FIG. here,
A two-time machining method will be described in which a rough machining (first cut) is followed by a second cut to correct the desired shape.

First, when machining is started as shown in step S11, the NC program is read, and a normal machining path corrected by a predetermined correction value is calculated according to the machining shape given by the NC program. do. As shown in Fig. 10, this normal machining path means that the machining path is corrected by offsetting the final shape by the sum of the wire diameter and machining gap, and the arc corners are machined by concentric circles of the program-shaped arc. This is to correct the route.

Next, in step S12, it is determined whether or not the locus to be machined is a corner portion. If the result of this determination is not a corner portion, the normal path correction calculated in step S11 is performed in step S13. Then, processing is executed in step S14. Further, if the determination result is a corner portion, the process moves to step S15 and the arc radius r of the corner portion is calculated. Next, in step S16, it is determined whether or not the current machining is the number of times of machining to newly convert the corner path. If the result of this determination is not the corresponding number of times, step S
13. If the determination result is the corresponding number of times, the process moves to step S17, where the radius r of the arc calculated in step S15 is compared with the reference radius R that is preset as a predetermined value, and the Radius r is reference radius R
If it is larger than , the process moves to step S13. If the radius r of the arc is less than or equal to the reference radius R, the process proceeds to step S18, and the machining path for the corner portion of the arc having the radius r is corrected by the method described below.

That is, in step S18, as shown in FIG. 9, first, in step S181, it is determined whether the corner portion is an outside corner or an inside corner, and then step S1
82. If the determination result in step S181 is an out corner, a first cut (current machining) path as shown in FIG. 11 is determined. However, this corner part has an arc radius r, the angle formed by the straight lines before and after the arc part is θ, and the straight line ■ is a bisector of two straight lines. By the way, since the shape shown by the broken line in the figure is obtained by the first cut, in order to correct the shape in the second cut (next processing) and finally finish it as the shape shown by the solid line, the apex of the corner of the shape obtained by the first cut must be set to a radius. The distance from the center Pr of the arc of r is arc radius r + machining gap g during second cut
2+wire electrode diameter d, or less. That is, the path of the first cut is further inside the point P which is separated by the machining gap g1 at the time of the first cut + half the wire electrode diameter d/2. Therefore, the straight line Pr
・P is determined by Equation 3.

[0042]

[Formula 3] Straight line Pr・P=r+g2+d+g1+d/2

0043
] If the result of step S181 is inside corner, a first cut (current machining) path as shown in FIG. 12 is determined. In other words, since the first cut results in the shape shown by the broken line in the figure, in order for the second cut (next processing) to achieve the final shape, the first cut shape (dashed line) must be inside the second cut shape (solid line). be. That is, the apex P of the arc of the first cut (current machining) path is closer to the center Pr of the arc r than the apex of the arc of the second cut shape by more than the first cut machining gap g1 + half d/2 of the wire electrode diameter. It must be in Therefore, the straight line Pr·P can be obtained using equation 4.

[0044]

[Formula 4] Straight line Pr・P=r−(g1+d/2)

[0045] If the point P is determined for the outside corner and the inside corner in the above manner, even if the "drop" is small, cutting off in the second cut (next machining) at the outside corner will not occur, and short circuits due to scrap will be avoided. In addition, at inside corners, overcuts and surfaces that cannot be machined in the second cut (next machining) are completely eliminated, and ``drops'' can be efficiently corrected.

Based on the point P found in step S182,
In step S183, as shown in FIGS. 11 and 12,
Find a circle that passes through point P and is tangent to straight lines L1 and L2 whose paths have been corrected with respect to the two straight lines before and after the circular arc part, and its contact point Ps2,
Find Pe2. Next, proceeding to step S184,
The final corrected route,

[0047] Straight line Ps1・Ps2→Circular arc Ps2・P・P
e2→calculate straight line Pe2 and Pe1. By the above method, the path is corrected by applying the smallest arc whose shape can be corrected in the next machining to the corner portion, and the machining is executed in the next step S19. The above operations are repeated until the end of the program, the next machining stage is similarly executed, and the machining is terminated when machining has been completed a predetermined number of times.

Next, taking as an example the case where the NC program shown in FIG. 13 is used to process the shape shown in FIG. 14,
The above process will be explained in more detail. In FIG. 13, (21) is the main program whose program name is indicated by L1000, and (22) is a variable expressed by H100 to which the total number of machining times for converting the corner part is substituted.
When 0=2, the first cut and second cut apply, and when H100=1, only the first cut applies. (23) and (25) are variables represented by H101 to which the number of machining is substituted, (24) and (26) indicate the NC data of the first cut and second cut, respectively, the character string F is the machining speed, and the character string E is the processing condition, variable H1
is a path correction value, and G22 is an instruction code for calling a subprogram. (27) has the program name L20
The subprogram indicated by 00 (28) is an instruction code for M80 to supply the machining fluid 4, M82 to feed the wire electrode 1, and M84 to turn on the machining power source 5, (2
9) is an instruction code for G41 to correct the machining path by the correction value indicated by the variable H1 on the left side with respect to the machining progress direction;
G01 is a command code that commands linear movement, G02 and G03 are command codes for circular movement, and (30), M85 is the processing power supply 5.
(31) is the command code for commanding the cutting of the wire electrode 1, M83 is the command code to cut off the feed of the wire electrode 1, and M81 is the command code for cutting off the supply of the machining fluid 4.
23, which is an instruction code for instructing a return to the main program L1000.

In order to process the shape shown in FIG. 14 by the second cut method, first the main program L1000 and the subprogram L20 are processed by the tape reader 103.
The contents of 00 are read and stored in the program memory 101. Subsequently, when execution of L1000 is instructed via the operation panel 108, the arithmetic processing unit 104a identifies the program based on the program name and executes the main program L1.
Processing of 000 is started based on the program data. Since the content of the variable H101 is set to "1" indicating the first machining, it is determined that this is the first cut machining. Next, determine the character string F, set the machining speed to a1, similarly set the machining condition to b1 from E, and set the machining speed to b1 using the variable H1.
Set c1 to set the route correction value (offset).

When G22 is determined by the arithmetic processing unit 104a, the subsequent subprogram L2000 is called, M80, M82, and M84 are determined, and the machining fluid 4 is supplied and the wire electrode 1 is fed. At the same time, a pulse voltage is applied between the wire electrode 1 and the workpiece 2, and relative movement between the wire electrode 1 and the workpiece 2 is started according to the next movement command, and electrical discharge machining is executed. .

That is, first, when instruction code G92 is determined, (X0, Y0) is set as the processing start point. The following instruction code G01 is determined, and the machining path is corrected to the left (outward in the shape of the figure) with respect to the machining progress direction by the amount c1 previously set in the variable H1 using the instruction code G41. Therefore, given as the amount of movement (△x1, △
y1) is corrected and input to the pulse distributor 107. The pulse distributor 107 executes pulse distribution calculation and distributes the X-axis and Y-axis distribution pulses to the X-axis servo unit 9a, respectively.
, is input to the Y-axis servo unit 9b, the X-axis servo motor 8a and the Y-axis servo motor 8b are rotated, the X-Y cross table 7 is moved, and processing is performed from P0 to P11 in FIG. 14. The next line is also G01, so the same process is performed, and P11→
Process the path of P21. And instruction code G02
At the time when the variable H101 is determined, it is determined whether the variable H101 has a value of variable 100 or less, and in this case, the variable H101 is "1".
” and the variable H100 is “2”, so △i, △
Calculate the radius r of the circular arc from j.

[0052]

[Formula 5]

Furthermore, the radius r is written in the radius data area of the work memory 105, the reference radius R input in advance in the variable memory 106 is compared with the arc radius r, and if r≦R, the following processing is performed. . First, in (29), the path is corrected to the left with respect to the machining progress direction by command code G41, and it is determined that it is a clockwise circular arc by command code G02, so from G41 and G02, the arc is out. It is determined that it is a corner. Therefore, by finding the point P according to Equation 3, corner parts P21 and P3
1 route correction is performed. At this time, g1, g2, and d are read from variable memory 106.

[0054] Thereafter, the machining is continued while similar processing is performed, but for example, in arcs P4 and P5, the arc radius r obtained from (△i5, △j5) satisfies R≦
If r, variable H101="1" and variable H10
Even if it is less than the value "1" of 0, the above-mentioned corner processing is not performed, and the arcs P4 and P5 are processed by normal path correction.

When the processing of the machining path information (29) shown in FIG. 13 is completed as described above, the machining power source 5 is turned off and the wire The feeding of the electrode 1 and the cutting off of the supply of the machining fluid 4 are commanded, the machining is stopped, and (31)
When G23 is determined as shown in the main program L
Return to 1000.

After that, the first cut ends according to the program, and the second cut starts, but as shown in (25) of the main program, by determining H101="2" in the variable memory 106,
In subsequent processing, processing is performed based on the machining path of the subprogram without performing corner conversion processing.

As described above, in the first cut (rough machining), corners with a predetermined radius or less are processed by applying the smallest arc that can be modified in the shape in the second cut, correcting the machining path, and machining after the second cut. If machining is performed using the method according to this embodiment in which the corner shape is finished by finishing machining, as shown in Fig. 6 shown earlier, even if the corner portion during rough machining has a certain amount of droop, the rough machining and finishing will be the same. It is possible to finish the desired corner shape without making a large offset difference during machining. In addition, since this method uses the smallest possible arc radius, there is a possibility that when modifying the shape (next machining), the outside corner may be cut off, or an overcut may occur at the inside corner where the shape cannot be corrected. do not have. Furthermore, when creating finishing machining information, there is no need to perform special corner processing, and there is no need to create separate programs for rough machining and finishing machining.

[0058] In the above embodiment, the processing up to the second cut was explained, but the same processing can be performed for the third cut and above, and according to the above calculation, the specified number of processing times to convert the arc radius of the corner part is , the machining gap g is normally g1>g2>g3...>gn (the subscript indicates the number of times of machining), so the relationship of the inserted arc radius r is r1<r
2<r3...<rn (the subscript indicates the number of machining operations) will always hold true, and as the number of machining increases, the arc will gradually become larger, and eventually it will be possible to finish it into the desired arc shape. Become.

[0059]

[Effect of the invention] According to the first invention and the fourth invention,
At the stage of rough machining that is performed prior to finishing machining, it is determined whether the radius of the circular arc part within the machining shape is a preset reference radius or not, and if it is less than the standard radius, the circular arc part is formed by two straight lines. Since the corner shape is converted into a corner shape for machining, "sagging" of the circular arc portion during rough machining is suppressed, and the circular arc portion within the machining shape can be finished with high precision and efficiency.

According to the second invention, the third invention, and the fifth invention, the radius of the circular arc portion within the machining shape is set to a preset reference radius at each stage of finishing after rough machining. For the following circular arc parts, in the first machining step, the circular arc parts are machined using a machining path formed by inserting a circular arc that is in contact with the machining path before and after the circular arc part and whose radius is smaller than a predetermined radius, and the subsequent machining By gradually increasing the radius of the circular arc to be inserted and correcting the machining path, the circular arc part is finally machined into the desired shape, so the "sagging" of the circular arc part during rough machining is suppressed. , it is possible to finish the circular arc portion within the processed shape with high precision and efficiency.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a numerical control device that implements an embodiment of the first and fourth inventions.

FIG. 2 is a flowchart illustrating the operation of an embodiment of the first and fourth inventions.

FIG. 3 is a diagram showing an NC program for explaining the operation of one embodiment of the first and fourth inventions.

FIG. 4 is a diagram showing a shape processed by the NC program of FIG. 3;

FIG. 5 is an enlarged view showing a local part of FIG. 4;

FIG. 6 is an explanatory diagram showing improvement in processing accuracy according to the present invention.

FIG. 7 is a block diagram of a numerical control device that implements an embodiment of the second, third, and fifth inventions.

FIG. 8 is a flowchart illustrating the operation of an embodiment of the second, third, and fifth inventions.

FIG. 9 is a flowchart illustrating a portion of FIG. 8 in detail.

FIG. 10 is a diagram showing path correction in normal (or conventional) machining.

FIG. 11 is a diagram showing path correction at an out corner portion according to an embodiment of the second, third, and fifth inventions.

FIG. 12 is a diagram showing path correction at an inside corner portion according to an embodiment of the second, third, and fifth inventions.

FIG. 13 is a diagram showing an NC program for explaining the operation of one embodiment of the second, third, and fifth inventions.

FIG. 14 is a diagram showing a shape processed by the NC program of FIG. 13;

FIG. 15 is a configuration diagram of a conventional wire electric discharge machining apparatus.

FIG. 16 is an explanatory diagram of "sloping" in edge corner portions.

FIG. 17 is an explanatory diagram of "sloping" in the arcuate corner portion.

FIG. 18 is an explanatory diagram of a problem in machining an arc corner portion using a conventional method.

[Explanation of symbols]

101 Program memory 104, 104a Arithmetic processing unit 105 Working memory 106 Variable memory 109 Machining condition memory

Claims (5)

[Claims] Claim 1: In a wire electrical discharge machining method in which rough machining is followed by finish machining to machine a workpiece into a predetermined shape, a reference radius is set in advance, and the result of determining whether or not rough machining is being performed. For rough machining, compare the radius of the circular arc part within the machining shape with the reference radius, and if the radius of the circular arc part is less than the reference radius, convert the circular arc part to a corner shape formed by two straight lines. A wire electrical discharge machining method characterized by machining. 2. In a wire electrical discharge machining method in which finishing machining is performed following rough machining to machine a workpiece into a predetermined shape, the radius of an arcuate portion within the machining shape is less than or equal to a preset reference radius. On the other hand, in the first machining, the above-mentioned circular arc part is machined by a machining path formed by inserting a circular arc that touches the machining path before and after this circular arc part and is smaller than a predetermined radius, and the radius of the circular arc inserted in the subsequent machining is A wire electrical discharge machining method characterized in that machining is performed while changing the machining path by gradually increasing the arc radius from the previously inserted arc radius. Claim 3: An arc smaller than the predetermined radius,
3. The method according to claim 2, wherein the arc is the smallest that can be corrected to a desired shape in the next machining based on the outer diameter of the wire electrode used, the current machining gap, and the next machining gap. Wire electrical discharge machining method. 4. A wire electrical discharge machining device that performs finishing machining following rough machining to machine a workpiece into a predetermined shape, comprising a discriminating means for determining whether or not rough machining is being performed, and a radius of a circular arc portion within the machining shape. and a preset standard radius, and if each of the above results indicates rough machining and the radius of the circular arc part is less than the standard radius, converts the circular arc part into a corner shape formed by two straight lines. A wire electrical discharge machining apparatus comprising: a conversion processing section that performs conversion; and an arithmetic processing unit that performs conversion. 5. A wire electrical discharge machining device that performs finishing machining following rough machining to machine a workpiece into a predetermined shape, comprising: a determining means for determining the number of machining operations; If the results from the comparison section, the determination means, and the comparison section are that the number of times of machining is a predetermined number and the radius of the arc section is less than or equal to the reference radius, the arc section is processed before and after the arc section. A wire electric discharge machining device comprising: a conversion processing section that converts the machining path into a machining path formed by inserting a circular arc that is in contact with the path and has a predetermined radius or less;