JP2008036720A - Wire electric discharge machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire electric discharge machine which corrects a deflection amount and highly accurately machining even when the deflection amount of a wire electrode is different depending on the moving direction of the wire electrode. <P>SOLUTION: The deflection amount of the wire electrode is measured (25) in the moving direction of the wire electrode, and stored in a storage means (26). The moving command of each axis is obtained (22) based on a machining program (21) and a machining speed in machining. The machining direction (moving direction of the wire electrode) is obtained by the moving command, and the deflection amount in the direction of each feed axis is estimated (23) based on the machining direction, the deflection amount in the direction stored in the storage means (26), and the moving speed of each axis at the time. The correction amount is obtained by the estimated deflection amount of each axis and the moving command to each axis corrected (24) respectively. Since the deflection amount is corrected based on the machining direction even if the deflection amount of the wire electrode is different depending on the machining direction, the deflection amount of the wire electrode is accurately corrected, and a highly accurate machining is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wire electric discharge machine, and more particularly to a wire electric discharge machine that corrects bending of a wire electrode during electric discharge machining.

The wire electric discharge machine stretches the wire electrode with the upper and lower wire guides, causes the wire electrode to approach the workpiece while applying a voltage between the wire electrode and the workpiece (workpiece), and generates electric discharge. Processing is performed by melting the workpiece in the vicinity of the wire electrode by the generated heat. The relative positions of the upper and lower wire guides and the workpiece (workpiece) are controlled so that the machining is performed according to the machining shape commanded by the machining program.
However, the wire electrode is a thin wire such as brass or copper, and the wire electrode has a property of being bent by the discharge pressure or the like when a discharge occurs. The bending position of the wire electrode shifts the processing position from the wire guide position, resulting in a decrease in processing accuracy.

  FIG. 13 is an explanatory diagram for explaining the state of the wire electrode during electric discharge machining. In FIG. 13, the work 3 is mounted on a work table 4, and the wire electrode 1 is stretched while being guided by an upper wire guide 2 a and a lower wire guide 2 b disposed above and below the workpiece 3. A voltage is applied between the workpiece 3 and the wire electrode 1, and the upper and lower wire guides 2a and 2b are moved relative to the workpiece 3, and the wire electrode 1 is made of brass or copper of about 0.1 to 0.3 mm. Therefore, the wire electrode 1 bends about several tens of microns in the direction opposite to the moving direction of the wire guide due to the influence of the discharge pressure or the like in the electric discharge machining portion of the wire electrode 1. FIG. 13 shows an example in which the upper and lower wire guides 2a and 2b are moved to the left as shown by arrows in the drawing with respect to the workpiece 3. Therefore, the wire electrode 1 moves at a position away from the wire guides 2a and 2b by a deflection amount. Even if the wire guides 2a and 2b are controlled and moved as instructed by the machining program, they are actually machined. The processed shape of the processed workpiece 3 is not a programmed processed shape. The shape error due to the bending of the wire electrode is conspicuous in the processing of the corner portion or the arc processing with a small radius. It is a phenomenon called so-called cornering.

  FIG. 14 is an explanatory diagram of this cornering. The wire electrode 1 is moved by being offset by the discharge gap ε with respect to the machining path (machining shape) 5 in which the 90-degree movement direction is commanded by the machining program. A central passage of the wire guides 2a and 2b is denoted by reference numeral 6. In the corner portion where the movement direction changes by 90 degrees as the wire electrode 1 bends in the direction opposite to the movement direction of the wire guides 2a and 2b, the center of the wire electrode 1 is indicated by a broken line 6 'as shown in FIG. , 2b through the moving path. As a result, as shown by a broken line 5 ', the machining shape becomes an inner path unlike the machining path 5 commanded by the machining program, and there is a problem that machining of the shape commanded by the machining program cannot be obtained.

  As a method of preventing this corner sagging, when the die shape is machined by eliminating the shape error due to the outer corner of the corner and the biting of the inner corner by performing extra cutting in the linear direction at the corner, That can smoothly fit products such as punches and punches (see Patent Document 1), and by reducing the processing pressure at the corners and reducing the discharge pressure to reduce the bending amount of the wire electrode, A method of improving (see Patent Documents 2 and 3) is known.

  In the processing of arcs and corners, the amount of bending in the tangential direction and the amount of bending in the radial direction of the arc are obtained, and the machining path is corrected (see Patent Document 4). A method of correcting the wire guide trajectory by obtaining the discharge voltage based on the instantaneous machining fluid pressure and fixed parameters (see Patent Document 5), and when the corner angle is an acute angle, a correction path with a pattern predetermined in the corner is added. And a method of machining the corner portion (see Patent Document 6), and a method of machining the corner portion by adding an auxiliary route to the program command route in the same manner (see Patent Document 7). It has been.

  Methods for measuring the amount of deflection of the wire electrode are known in the above-mentioned Patent Documents 4 and 8. In this deflection amount measuring method, processing is performed at a predetermined processing speed under specified processing conditions, and processing is stopped in the middle of the processing. Since the machining is stopped and the discharge is stopped, the discharge pressure is lost, and the wire electrode and the workpiece are short-circuited. This is detected by a short-circuit detection device, the wire electrode is retracted until the short-circuit is released, the retracted distance is determined, and the deflection of the wire electrode is determined from the retracted distance and the discharge gap amount under the processing conditions.

  FIG. 15 is an explanatory diagram of a method of measuring the wire electrode deflection amount. In FIG. 15, it is assumed that the wire guides 2a and 2b are moving in the right direction. During the electric discharge machining, the electric discharge machining is performed with the wire electrode 1 and the work 3 being separated by a predetermined discharge gap amount ε, and is stretched between the upper and lower wire guides 2a and 2b. The wire electrode 1 is subjected to electric discharge machining while being bent by electric discharge pressure or the like. When machining is stopped and electric discharge is stopped in this state, the wire electrode comes into contact with the workpiece 3 as indicated by reference numeral 1 'in FIG. Therefore, the wire guides 2a and 2b are moved backward relative to the workpiece 3 (the direction opposite to the advancing direction at the time of machining so far), and the position where the contact between the wire electrode 1 and the workpiece 3 is released, that is, short circuit detection. The apparatus is retracted to a position where the wire electrode 1 and the work 3 are short-circuited. If this backward movement amount is L, in this wire guide 2a, 2b, the wire electrode 1 is the position where the contact with the workpiece 3 is removed, and the wire electrode 1 'in FIG. The electrode 1 is linear without bending between the wire guides 2a and 2b. However, during the electric discharge machining, the wire electrode 1 and the workpiece 3 are further separated by a predetermined electric discharge gap amount ε, which indicates that during the electric discharge machining, the wire electrode 1 and the workpiece 3 are bent by “L + ε”. ing. Therefore, the deflection amount D0 of the wire electrode 1 can be obtained from the amount of backward movement L and the discharge gap amount ε determined by the processing conditions.

Japanese Patent Laid-Open No. 2-100826 Japanese Patent Publication No. 2-5531 Japanese Patent Publication No. 2-11371 Japanese Examined Patent Publication No. 1-44451 Japanese Patent Laid-Open No. 10-34443 JP-A-11-207527 JP-A-11-221719 Japanese Examined Patent Publication No. 62-53293

  In order to improve the machining accuracy in wire electric discharge machining, it is important to reduce the shape error due to the bending of the wire electrode. In the method of eliminating the shape error by adding the cutting process at the corner as described in Patent Documents 1 and 7 described above, a process other than the commanded shape is performed, and the die of the punching die is used. It is limited to processing or the like. In addition, the method of reducing the processing speed at the corner portion described in Patent Documents 2 and 3 to reduce the deflection amount of the wire electrode and improving the processing accuracy has a problem that the processing time becomes long, and the processing If the speed is too low, the discharge gap may increase and conversely occur.

Further, in the method of estimating the wire electrode deflection amount described in Patent Documents 5 and 6 and correcting the machining path with this estimated deflection amount, if the wire electrode deflection amount cannot be accurately estimated, the wire electrode is left uncut and cut. There is a problem that occurs.
Conventionally, the amount of bending of the wire electrode is constant regardless of the direction of movement of the wire guide. However, the present inventors have found that the amount of bending of the wire electrode varies depending on the moving direction of the wire guide. The wire electrode delivery reel and the take-up reel are attached to the column of the wire electric discharge machine, and the wire electrode delivery and movement in the winding direction are affected by the elastic deformation of the wire electrode, The change is great. From this, it is necessary to consider the moving direction of the wire guide (the relative moving direction of the wire electrode with respect to the workpiece) in order to accurately estimate the bending amount of the wire electrode.

  Accordingly, an object of the present invention is to provide a wire electric discharge machining capable of correcting the position of the wire electrode and performing high-precision machining by estimating the deflection amount of the wire electrode in consideration of the moving direction of the wire electrode. .

  In the invention according to claim 1 of the present invention, a wire electrode is stretched between the upper and lower wire guides, and a discharge is generated by causing the wire electrode to approach the workpiece while a voltage is applied between the wire electrode and the workpiece. In a wire electric discharge machine that performs electric discharge machining by controlling the machining speed based on the discharge state and measuring the amount of deflection of the wire electrode measured for each relative movement direction of the wire guide with respect to the workpiece Notified from the deflection amount storage means, the machining program stored in the machining program storage means, the means for determining the relative movement command of the wire guide and the workpiece from the machining program and the machining speed, and the relative movement command determination means. Means for estimating the actual wire electrode deflection amount based on the relative movement command and the measured deflection amount stored in the measured deflection amount storage means; It shall comprise means for correcting the position of the wire guide based on the estimated amount of deflection of the electrode, even if the deflection amount of the wire electrode is changed by the processing direction can accurately deflection correction, thereby improving the machining accuracy.

  The invention according to claim 2 is a means for estimating the amount of deflection of the wire electrode, and estimates the amount of deflection in the direction of the feed axis for each feed axis that moves the wire guide relative to the workpiece. The means for correcting the position of the wire guide corrects the movement command to each feed axis based on the estimated deflection amount for each feed axis. Furthermore, in the invention according to claim 3, the measured deflection amount storage means stores the measured deflection amount of the wire electrode for each forward and reverse movement direction of each feed shaft for moving the wire guide relative to the workpiece. I did it.

  In the invention according to claim 4, the means for estimating the actual amount of deflection of the wire electrode estimates the amount of deflection of the wire electrode from the processing speed when the measured amount of deflection of the wire electrode is measured and the actual processing speed. It was supposed to be. According to a fifth aspect of the present invention, the wire electric discharge machine is provided with means for measuring the deflection amount of the wire electrode with respect to the moving direction of the wire guide.

  Since the correction amount of the wire electrode deflection is obtained and corrected based on the machining direction, even if the deflection of the wire electrode varies depending on the machining direction, the deflection can be accurately corrected. Therefore, highly accurate wire electric discharge machining can be performed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view for explaining the outline of the wire electric discharge machine of the present embodiment. A wire electrode delivery reel 10 and a wire electrode take-up reel 11 are provided in a column or the like of the wire electric discharge machine, and the wire electrode 1 delivered from the wire electrode delivery reel 10 is guided by an upper wire guide 2a via a guide roller 13. Then, it passes through the processed portion of the work 3 placed and attached to the work placing table 4, is guided by the lower wire guide 2 b, and is taken up by the wire electrode take-up reel 11 through the guide roller 14. . The work table 4 to which the work 3 is attached is driven in the X-axis and Y-axis directions orthogonal to each other by the X-axis servomotor Mx and the Y-axis servomotor My. Further, the upper wire guide 2a is driven in the Z-axis direction orthogonal to the X and Y axes by the Z-axis servo motor Mz so that the position of the upper wire guide 2a can be adjusted by the thickness of the work 3 and the like. . Further, the upper wire guide 2a is driven in the U and V axis directions orthogonal to each other by the U axis servo motor Mu and the V axis servo motor Mv, thereby enabling the workpiece 3 to be tapered.

  A voltage is applied between the wire electrode 1 and the work 3 from the electric discharge machining power source 30 via the power supply roller 12, and an electric discharge is generated between the wire electrode 1 and the work 3 to perform electric discharge machining. Further, a short circuit detection device 31 is also connected between the wire electrode 1 and the workpiece 3 so as to detect a short circuit, that is, contact between the wire electrode 1 and the workpiece 3. Reference numeral 20 denotes a control device of the wire electric discharge machine, and in this embodiment, is constituted by a numerical control device. This control device 20 outputs a movement command to each of the X, Y, Z, U, and V axis servo motors Mx, My, Mz, Mu, and Mv to move the workpiece 3 relative to the wire electrode 1 for machining. I do. Further, the machining speed is obtained by the electric discharge machining power source 30 and is input to the control device 20. In addition, when detecting a contact or short circuit between the wire electrode 1 and the work 3, a short circuit detection signal is input from the short circuit detection device 31. Reference numeral 15 denotes a nozzle that supplies cooling water to the electric discharge machining region.

  In addition, since the structure of the wire electric discharge machine mentioned above is the same as that of the conventional wire electric discharge machine, it is schematically shown in FIG. Further, as described above, in this embodiment, it is also possible to perform taper processing by unevenly locating the upper and lower wire guides 2a and 2b by driving and controlling the U-axis and V-axis servomotors Mu and Mv. However, in order to simplify the description, the case of vertical machining in which the upper and lower wire guides 2a and 2b are in the same position will be described below. Furthermore, relative movement of the workpiece 3 with respect to the wire guides 2a and 2b may control either movement of the wire guides 2a and 2b or the workpiece 3. In the example shown in FIG. Although shown, an example in which the wire guides 2a and 2b are moved will be described below for easy understanding and simplicity.

FIG. 2 is a functional block diagram showing the control function of the control device 20 in the present embodiment.
Compared with the control device of the conventional wire electric discharge machine, the wire electrode deflection amount estimating means 23, the wire electrode deflection correction means 24, the wire electrode deflection amount measuring means 25 for each moving direction, and the wire electrode deflection amount storing means 26 for each moving direction are provided. This is different from the conventional one.
In the wire electric discharge machine, the discharge state between the wire electrode 1 and the workpiece 3 is monitored, and the wire electrode is moved relative to the workpiece at an optimum processing speed based on this discharge state. For monitoring the discharge state, usually, the gap voltage between the wire electrode and the workpiece is detected, and the wire electrode 1 is moved relative to the workpiece 3 by servo feed control for controlling the machining speed so that the gap voltage becomes constant. The method of letting it be common is. Furthermore, the number of discharges per unit time generated between the wire electrode 1 and the work 3 and the integrated value of the discharge current are monitored, and the machining speed is controlled so that the number of discharges and the integrated value of the discharge current become predetermined values. A method to do this has also been developed. In the example shown in FIG. 1 and FIG. 2, an example is shown in which the discharge state is monitored by the electric discharge machining power source 30 and is notified to the control device that obtains the machining speed. The number of discharges per unit time, the discharge current integrated value, and the like are detected and transmitted to the control device 20, and the control device 20 processes the machining speed based on the gap voltage, the number of discharges per unit time, and the discharge current integrated value. May be obtained.

  In any case, the processing speed (the relative feed speed of the wire electrode 1 to the work 3 and substantially the feed speed of the upper and lower wire guides 2a and 2b to the work 3) is controlled by the discharge state. Yes, when the wire electrode 1 and the workpiece 3 are short-circuited, the machining speed is set to a negative value, and so-called backward control is performed to reverse the wire electrode 1 along the machining path. In addition, control such as lowering the machining speed at the same time as lowering the machining conditions in the corner machining unit is performed. Therefore, the bending amount D of the wire electrode during processing varies depending on the processing speed. In addition, as described above, due to the feeding and winding direction of the wire electrode, the deflection amount D of the wire electrode varies depending on the feeding direction of the wire electrode. For example, when the wire electrode is fed and wound in the X-axis direction, the deflection amount D is large when the wire electrode is moved in the X-axis direction. For this reason, in this embodiment, the bending amount D of the wire electrode is estimated for each feeding direction.

  Then, the bending amount D of the wire electrode is processed at a processing speed F0 by test processing, and when the bending amount at that time is D0, and at the processing speed F in actual processing, the following (1) The amount of deflection D is estimated by the equation.

D = D0 · Func (F / F0) (1)
The function Func here may be obtained experimentally by performing test machining while changing the machining speed. FIG. 3 is a graph showing an example of the function Func obtained by test processing.
Therefore, in this embodiment, the amount of deflection D0 at a predetermined speed F0, which serves as a reference for estimating the amount of deflection D, is measured by the wire direction deflection amount measuring means 25 for each direction of movement, and this measured amount of deflection is classified by direction of movement. It is assumed that the wire electrode deflection amount storage means 26 is stored. In addition, as described above, the amount of deflection D varies depending on the relative movement direction of the upper and lower wire guides 2a, 2b (wire electrode 1) with respect to the workpiece 3, and therefore, this reference amount is different for each of the X axis and Y axis directions of the feed axis. Measure and store the amount of deflection.

  This method of measuring the amount of wire electrode deflection is known and conventionally performed in Patent Documents 4 and 8 described above. In the present embodiment, this deflection amount measurement method is performed for each axis in the relative feed direction of the upper and lower wire guides 2a, 2b with respect to the work 3, that is, according to the conventional method implemented in FIG. This is performed for each of the X axis and the Y axis, and the amount of bending in the X axis direction and the amount of bending in the Y axis direction are obtained.

  In this measuring method, as explained with reference to FIG. 15, the upper and lower wire guides 2a and 2b (wire electrode 1) with respect to the workpiece 3 are moved at a predetermined speed F0 to perform electric discharge machining, and the machining is stopped while the machining is stable. Then, the discharge is stopped, and the upper and lower wire guides 2a and 2b are moved backward in the direction opposite to the current traveling direction to the position where the short circuit between the wire electrode 1 and the work 3 is taken by the short circuit detection device 31. The backward movement amount L to the position where the short circuit is released is obtained, and the deflection amount D is obtained by adding the discharge gap amount ε determined by the processing conditions to the movement amount.

D = L + ε (2)
In the present embodiment, the amount of deflection D is obtained for each feed direction of the feed axes X-axis and Y-axis. FIG. 7 is a flowchart showing an algorithm of wire direction deflection amount measurement processing for each moving direction performed by the processor of the control device 20 as the wire direction deflection amount measuring means 25 for each moving direction.

  The wire electrode deflection amount measurement for each moving direction can be executed by inputting a wire electrode deflection amount measurement command for each moving direction from an input means (not shown) to the control device 20, but an auxiliary function (for example, If it is automatically performed by instructing M80), it is possible to measure the amount of bending of the wire electrode that meets the actual processing conditions.

  When the wire direction deflection amount measurement command for each moving direction is input, the processor of the control device 20 starts the process shown in FIG. First, the X-axis servo motor Mx is driven under a predetermined machining condition, and the electric discharge machining is performed by moving the servo motor Mx in the X-axis + direction at a predetermined machining speed F0x +. The X-axis servo motor Mx is reversely rotated to retract the wire guides 2a and 2b, and the short-circuit detecting device 31 obtains the backward movement amount L until the short-circuit is no longer detected, and the discharge gap amount ε determined by the machining conditions Are added to obtain a deflection amount D0x + when moving in the X-axis + direction, and the memory as the wire electrode deflection amount storage means 26 for each moving direction is stored in the memory as shown in FIG. 4 with the processing direction X + and the processing speed F0x +. And the obtained measured deflection amount D0x + is stored (step 100). In this case, since the direction of bending of the wire electrode 1 is a negative direction, a negative value is stored as the bending amount D0x + stored in the wire electrode bending amount storage means 26 for each moving direction.

Next, the X-axis servo motor Mx is driven in the X-axis direction at a predetermined machining speed F0x-, the deflection amount D0x- is measured in the same manner, and the machining direction X- and the machining speed are measured as shown in FIG. D0x− and the obtained measured deflection amount D0x− are stored in the wire electrode deflection amount storage means 26 for each moving direction (step 101). In this case, since the deflection direction of the wire electrode 1 is a positive direction, a positive value is stored as the deflection amount D0x− stored in the wire electrode deflection amount storage unit 26 for each moving direction.
Further, the Y-axis servo motor My is driven in the Y-axis + direction at a predetermined machining speed F0y +, and the deflection amount D0y + is measured in the same manner. The machining direction Y +, the machining speed F0y + (negative value), and the measured deflection amount D0y + In addition, the Y-axis servo motor My is driven in the Y-axis minus direction at a predetermined machining speed F0y-, and the deflection amount D0y- is measured in the same manner, the machining direction Y-, the machining speed F0y-, and the measured deflection amount. D0y− (positive value) is stored in the wire direction deflection amount storage means 26 for each moving direction (steps 102 and 103). If the machining feed rate is the same speed F0 (= F0x + = F0x- = F0y + = F0y-) regardless of whether the axis is different or the direction is different, this speed F0 is: It is not always necessary to store the wire electrode deflection amount storage means 26 for each moving direction. In this case, what is necessary is just to memorize | store the bending amount corresponding to a process direction and this direction.

In this way, the bending amount for each moving direction as shown in FIG. 4 is obtained and stored in the wire electrode bending amount storage means 26 for each moving direction, and then actual machining is started.
In actual machining, based on the machining program stored in the machining program storage means 21 and the machining speed obtained by the electric discharge machining power supply 30, the wire guide movement command determination means 22 performs a predetermined cycle (distribution cycle) as in the prior art. ) A movement command for each movement amount is obtained and output to the X and Y axis servo motors Mx and My of the feed axes, and the X and Y axis servo motors Mx and My are driven to perform electric discharge machining. The movement command corrected by adding the wire electrode deflection correction amount to the movement command is output to the servo motors Mx and My.

The wire electrode deflection correction amount is estimated for each feed axis by the wire electrode deflection amount estimation unit 23, and the wire electrode deflection amount correction unit 24 is configured to correct the movement command of the X and Y axes of each feed axis. .
The wire electrode deflection amount estimation means 23 obtains velocity components Fx and Fy for each feed axis based on each axis movement command amount output from the wire guide movement command determination means 22 for each predetermined period (each distribution period). That is, if the movement command to the X axis in the predetermined cycle (distribution cycle) T obtained by the wire guide movement command determination means 22 is Δx and the movement command to the Y axis is Δy, the movement speed of the X and Y axes is
Fx = Δx / T
Fy = Δy / T
As required. The X and Y axis movement commands Δx and Δy have signs, and the X and Y axis movement speeds Fx and Fy also have signs. Based on the speed components Fx and Fy thus obtained and the machining speed and the deflection amount for each machining direction stored in the wire electrode deflection amount storage means 26 for each moving direction, the calculation of the above-described equation (1) is performed to obtain each feed axis. Find the amount of correction for each. For example, when the velocity components Fx and Fy are both in the + direction, is as follows.

Dx = D0x + · Func (Fx / F0x +)
Dy = D0y + ・ Func (Fy / F0y +)
When the deflection correction amounts Dx and Dy for each feed axis are thus estimated by the wire electrode deflection amount estimation means 23, the wire electrode deflection correction means 24 corrects the movement command of each axis. As shown in FIG. 5, in the correction process in FIG. 5, since the wire electrode 1 is separated from the wire guide in the movement direction rearward by the amount of bending, the wire guides 2a and 2b may be advanced by that amount. That is, the vectors (−Dx, −Dy) for moving the wire guides 2 a and 2 b by the deflection amounts Dx and Dy of the wire electrode 1 in the movement direction become the deflection correction vectors of the wire electrode 1.

  However, even if the moving direction of the wire guides 2a and 2b changes suddenly, the actual deflection of the wire electrode 1 cannot follow, so it is necessary to limit the amount of change in the deflection correction vector of the wire electrode 1. FIG. 6 is an explanatory diagram for limiting the amount of change in the deflection correction vector.

  In FIG. 6, assuming that the correction vector in the previous cycle is Vold and the correction vector in the cycle is Vnew, if the change amount Ddif of the difference between the two vectors Vold and Vnew exceeds the predetermined limit value Dlim, By using the correction vector Vnew in the above as a correction vector in which the correction vector in the previous cycle has changed from Vold by the limit value Dlim, a sudden change is prevented.

  FIG. 8 is a flowchart showing an algorithm of wire electrode deflection amount estimation processing performed by the processor of the control device 20 every predetermined cycle (distribution cycle) as the wire electrode deflection amount estimation means 23.

First, the movement amount Δx of the movement command to the X axis of each feed axis and the movement amount Δy of the movement command to the Y axis in the cycle obtained by the wire guide movement command determination means 22 based on the machining program and the machining speed. Is divided by a predetermined period (distribution period) T for obtaining the movement amount, and the X-axis and Y-axis velocity components Fx and Fy are obtained (step 200). Next, in accordance with the sign of the X-axis feed speed component Fx, the X-axis machining speed F0x (= F0x + or F0x−) and the deflection amount D0x (= D0x + or D0x−) is read out (step 201), and the X-axis direction wire electrode deflection amount Dx is obtained by calculating the equation (1). That is,
Dx = D0x · Func (Fx / F0x)
(Step 202).

  The Y-axis machining speed F0y (= F0y + or F0y-) and the deflection amount D0y (= D0y + or D0y-) stored in the wire electrode deflection amount storage means 26 for each moving direction in accordance with the sign of the Y-axis feed rate Fy. ) Is read out (step 203), and the axial wire electrode deflection amount Dx is obtained by calculating the equation (1) (step 204).

Dy = D0y · Func (Fy / F0y)
The X and Y axis direction wire electrode deflection amounts Dx and Dy thus obtained are output to the wire electrode deflection amount correction means 24 (step 205).

Note that the data stored in the movement direction-specific wire electrode deflection amount storage means 26 is only the machining direction (movement direction) and the deflection amount D, and the machining speed (feed rate) when this deflection amount D is obtained is the machining direction ( Regardless of the moving direction), if the wire electrode deflection amount storage means 26 for each moving direction is not stored at the predetermined speed F0, the wire electrode deflection amount D in each axial direction is as follows in steps 202 and 204: Is required.
Dx = D0x · Func (Fx / F0)
Dy = D0y · Func (Fy / F0)
FIG. 9 shows a wire electrode deflection correction process performed by the processor of the controller 20 as the wire electrode deflection correction means 24 at the same period as the period (distribution period) of the wire electrode deflection amount estimation process shown in FIG. It is a flowchart which shows an algorithm.

The wire electrode deflection amounts Dx and Dy sent in the step 205 of the wire electrode deflection amount estimation means 23 are reversed, and the new wire electrode is set as Dxnew = −Dx, Dynew = −Dy. Correction vectors (Dxnew, Dynew) are obtained and stored in a register (step 300).
From the obtained new wire electrode correction vector (Dxnew, Dynew) and the wire electrode correction vector (Dxold, Dyold) of the previous period stored in the register, the differences Dxdif, Dydif are obtained (step 301).
Dxdif = Dxnew-Dxold
Dydif = Dynew-Dyold
The difference distance Ddif is obtained (step 302).

Ddif = √ (Dxdif ² + Dydif ² )
The obtained distance Ddif is compared with a preset limit value Dlim for wire electrode deflection correction. If the obtained distance Ddif is less than or equal to the limit value Dlim, the process proceeds to step 305 and the obtained distance Ddif is the limit value. If it exceeds Dlim, the process proceeds to step 305 after performing the process of step 304.

In step 304, a difference vector whose magnitude is the limit value Dlim in the direction of the difference vector between the new wire electrode correction vector (Dxnew, Dynew) and the wire electrode correction vector (Dxold, Dyold) of the previous period Such a limited wire electrode deflection correction vector is obtained and set as new wire electrode correction vectors (Dxnew, Dynew).
(Dxnew, Dynew) = (Dxold, Dyold) + (Dxdif, Dydif) × (Dlim / Ddif)
The new wire electrode correction vector stored in the register is replaced with the limited wire electrode deflection correction vector (Dxnew, Dynew) thus obtained. If the obtained distance Ddif is equal to or smaller than the limit value Dlim, the new wire electrode correction vector (Dxnew, Dynew) obtained in step 300 is the new wire electrode correction vector as it is.

  Each axial component (Δx, Δy) of the difference between the obtained new wire electrode correction vector (Dxnew, Dynew) and the previous period wire electrode correction vector (Dxold, Dyold) is obtained, and the wire electrode deflection correction amount in each axial direction is obtained. The movement command to each axis is corrected by this correction amount and the servo motors Mx and My of each axis are driven (step 305).

δx = Dxnew−Dxold
δy = Dynew−Dyold
Next, the new wire electrode correction vector (Dxnew, Dynew) is stored in the register as the wire electrode correction vector (Dxold, Dyold) of the previous cycle, and the processing of the processing cycle ends.

Dxold = Dxnew
Dyold = Dynew
Thus, the wire electrode deflection correction amount is obtained for each of the X axis and Y axis movement directions of the feed axis, the movement command to each axis is corrected by this correction amount, and the X, Y axis is corrected by the corrected movement command. The servomotors Mx and My are controlled and driven. As a result, the deflection of the wire electrode can be accurately corrected.
FIG. 10 is an explanatory diagram of the movement paths of the wire guides 2a and 2b and the wire electrode 1 when the wire electrode deflection correction is performed at the corner portion that bends 90 degrees. The wire electrode 1 is an example in which the corner portion is processed by moving in the X-axis direction, and then moving in the Y-axis direction by changing the movement direction by 90 degrees. When the bending point of the corner portion is reached, the wire electrode 1 is bent in the X-axis direction, the center point of the wire guides 2a and 2b is at the position P1, and the bent wire electrode 1 is at the position Q1. . The correction vector is V1. Therefore, when the moving direction of the wire electrode 1 changes from the X-axis direction to the Y-axis direction, the correction vectors obtained in step 300 are Dxnew = 0 and Dynew = D0y. In FIG. 10, this is indicated as V ′. Since the distance of the difference between the correction vectors V 1 and V ′ is large, a new limited correction vector is obtained in step 304. This correction vector is, for example, V2 in FIG. In the following, the correction vector becomes V3, V4,... And the wire electrode 1 moves as Q1, Q2, Q3,..., The deflection correction amount in the X-axis direction becomes 0, and moves to the position of P2. Will move in the direction.

  FIG. 11 is a diagram illustrating a movement path of the wire guides 2a and 2b and the wire electrode 1 when the corner portion is an arc. In this case as well, the wire guides 2a and 2b and the wire electrode 1 move in the same manner as the 90 ° bent corner portion shown in FIG. 10, and only the points resulting from the point where the corner portion commanded by the program is an arc. Are different.

  In the above-described embodiment, a method of measuring and storing the wire electrode deflection amount for each direction (each movement direction is different by 90 degrees) for each feed axis that moves the wire electrode relative to the workpiece has been disclosed. However, the wire deflection amount may be estimated with higher accuracy by measuring and storing the deflection amount for each predetermined angle of the feeding direction (movement direction, machining direction). For example, by measuring and storing the feeding direction every 45 degrees, it is possible to estimate the wire deflection amount with higher accuracy. In the case of this embodiment, the wire direction deflection amount measurement processing for each moving direction shown in FIG. 7 measures the amount of deflection by changing the moving direction every 45 degrees. That is, X axis + direction (angle θ = 0 degrees), X axis + and Y axis + 45 degrees direction (θ = 45 degrees), Y axis + direction (θ = 90 degrees), X axis-and Y axis + 45-degree direction (θ = 135 degrees), X-axis-direction (θ = 180 degrees), X-axis-Y-axis 45-degree direction (θ = 225 degrees), Y-axis-direction (θ = 270 degrees), the deflection amount in 8 directions in the direction of 45 degrees (θ = 315 degrees) of the X axis + and the Y axis − is measured for each direction, and the wire electrode deflection amount storage means 26 for each moving direction is measured. . In this case, the machining speed (feed speed) F is assumed to be the same speed F0 even if the moving direction is different.

The deflection amount estimation processing by the wire electrode deflection amount estimation means 23 is changed to the processing of FIG. 12 instead of the processing shown in FIG.
First, the movement direction θ (= tan ⁻¹ (Δy / Δx)) is obtained from the movement amount Δx of the movement command to the X axis of each feed axis and the movement amount Δy of the movement command to the Y axis in the cycle, By dividing the movement amount by a predetermined period (distribution period) T, X-axis and Y-axis velocity components Fx and Fy are obtained (step 400). Next, the deflection amount D0 in the movement direction θ is obtained from the wire electrode deflection amount for each movement direction stored in the movement direction-specific wire electrode deflection amount storage means 26. If the amount of bending in the same direction as the moving direction θ is stored in the wire direction bending amount storage means 26 for each moving direction, the value is set as the amount of bending D0, and if not stored, the value is stored before and after the moving direction θ. The amount of deflection D0 in the moving direction θ is determined by interpolation from the amount of deflection in the angle. For example, if θ = 30 °, the deflection in the moving direction θ = 30 ° is obtained by interpolation using the deflection amounts of θ = 0 ° and θ = 45 ° stored in the wire electrode deflection amount storage unit 26 for each moving direction. A quantity D0 is calculated (step 401).

Next, based on the moving direction θ, the obtained deflection amounts D0 are calculated as deflection amount components D0x and D0y in the X-axis direction and the Y-axis direction.
The amount of deflection is obtained from each axis velocity component Fx, Fy obtained in step 400, each axis deflection amount component D0x, D0y obtained in step 402, the feed rate F0 at the time of wire electrode deflection amount measurement processing for each moving direction, and the moving velocity. Based on the function, the deflection amounts Dx and Dy of each axis are obtained (steps 403 and 404).

Dx = D0x · Func (Fx / F0)
Dy = D0y · Func (Fy / F0)
The X and Y axis direction wire electrode deflection amounts Dx and Dy thus obtained are output to the wire electrode deflection amount correction means 24 (step 405).

  The wire electrode deflection correction processing by the wire electrode deflection correction means 24 is the same as that of the first embodiment, and the same processing as the processing flowchart shown in FIG. 9 is performed to perform wire electrode deflection correction.

  Further, in each of the above-described embodiments, only the case of vertical machining has been disclosed. However, if the same wire electrode deflection correction is performed independently in the movement direction of the upper and lower wire guides, it can be easily applied to taper machining. is there.

It is explanatory drawing explaining the outline | summary of one Embodiment of the wire electric discharge machine of this invention. It is a functional block diagram which shows the control function of the control apparatus in the embodiment. It is explanatory drawing of the function which shows the relationship between the processing speed and wire bending amount in the embodiment. It is explanatory drawing of the memory content of the wire electrode deflection amount memory | storage means according to a moving direction which memorize | stores the wire electrode deflection amount for every process direction in the embodiment. It is explanatory drawing which calculates | requires the bending correction vector of a wire electrode from the bending amount of the wire electrode in the embodiment. It is explanatory drawing explaining the restriction | limiting of the variation | change_quantity of the deflection | deviation correction vector in the embodiment. It is a flowchart which shows the algorithm of the wire electrode deflection amount measurement process according to movement direction in the embodiment. It is a flowchart which shows the algorithm of the wire electrode deflection amount estimation process which the processor of the control apparatus in the same embodiment implements for every predetermined period. It is a flowchart which shows the algorithm of the wire electrode deflection amount correction process which the processor of the control apparatus in the embodiment implements for every predetermined period. When the wire electrode deflection correction of the present invention is performed at a corner portion bent by 90 degrees, it is an explanatory diagram of a wire guide and a movement path of the wire electrode. When a corner part is a circular arc, it is a figure which shows the movement path | route of a wire guide and a wire electrode at the time of performing wire electrode deflection | deviation correction | amendment of this invention. It is a flowchart which shows the algorithm of the wire electrode deflection amount estimation process which the processor of the control apparatus in the 2nd Embodiment of this invention implements for every predetermined period. It is explanatory drawing explaining the state of the wire electrode in electrical discharge machining. It is explanatory drawing of the corner sagging in the corner part process by the bending of a wire electrode. It is explanatory drawing of the measuring method of a wire electrode deflection amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wire electrode 2a Upper wire guide 2b Lower wire guide 3 Work piece 4 Work place stand 5 Processing path 6 Wire guide center passage 10 Wire electrode feed reel 11 Wire electrode take-up reel 12 Feed roller 13, 14 Guide roller 15 Cooling water nozzle Mx X axis servo motor My Y axis servo motor Mz Z axis servo motor Mu U axis servo motor Mv V axis servo motor 20 Controller (Numerical controller)
30 Electric discharge machining power supply 31 Short-circuit detection device

Claims (5)

A wire electrode is stretched between the upper and lower wire guides, a voltage is applied between the wire electrode and the workpiece, the wire electrode is brought close to the workpiece, a discharge is generated, the discharge state is monitored, and the discharge state is based on the discharge state. In a wire electrical discharge machine that performs electrical discharge machining by controlling the machining speed,
A measurement deflection amount storage means for storing a measurement deflection amount of the wire electrode measured for each relative movement direction of the wire guide with respect to the workpiece;
A machining program stored in the machining program storage means;
Means for determining a relative movement command of the wire guide and the workpiece from the machining program and the machining speed;
Means for estimating the actual deflection amount of the wire electrode based on the relative movement command notified from the relative movement command determining means and the measured deflection amount stored in the measured deflection amount storage means;
A wire electric discharge machine provided with means for correcting the position of the wire guide based on the estimated deflection amount of the wire electrode.   The means for estimating the actual amount of deflection of the wire electrode estimates the amount of deflection in the direction of the feed axis for each feed axis that moves the wire guide relative to the workpiece, and corrects the position of the wire guide. The wire electric discharge machine according to claim 1, wherein the means corrects a movement command to each feed axis based on an estimated deflection amount for each feed axis.   3. The measurement deflection amount of the wire electrode is stored in the measurement deflection amount storage means for each forward and reverse movement direction of each feed shaft that moves the wire guide relative to the workpiece. The wire electric discharge machine described in 1.   The means for estimating the actual deflection amount of the wire electrode estimates the deflection amount of the wire electrode from the machining speed when the measured deflection amount of the wire electrode is measured and the actual machining speed. The wire electric discharge machine of Claim 1. The wire electric discharge machine according to any one of claims 1 to 4, further comprising means for measuring a deflection amount of the wire electrode with respect to a moving direction of the wire guide.

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