JP2005199358A - Wire-cut electric discharge machining method, control method for wire-cut electric discharge machining, and wire-cut electric discharge machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that machining can not be executed at a set cone angle due to the occurrence of errors of the position of a wire electrode caused by a clearance of a wire guide. <P>SOLUTION: The wire-cut electric discharge machining device is provided with mobile bodies 48, 50, 56, and 58, a pair of the wire guides 3, 4, a movement controller 46 for executing positioning control of the mobile bodies, and a numerical controller 44. A calculation device 200 obtains a coordinate position of each interpolation position in numerical control of the wire electrode 1 by analyzing a machining program and also obtains a coordinate position of the wire guide 3(4) corresponding to the coordinate position of the wire electrode 1. The calculation device 200 calculates a horizontal distance between the wire guides 3, 4 on the basis of the coordinate position of the wire guide 3(4). The calculation device 200 also calculates a horizontal corrected coordinate position of the wire guide 3(4) from the coordinate position of the wire guide 3(4), the horizontal distance, and the one side clearance, and outputs movement data to the movement controller 46 after calculating them. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wire-cut electric discharge machining that prevents a reduction in machining shape accuracy caused by an error in the position of a wire electrode caused by a clearance of a wire guide during machining by correcting the horizontal position of the wire guide. In particular, the present invention relates to wire-cut electric discharge machining that corrects the horizontal position of the wire guide so that the inclination angle of the actual wire electrode being machined becomes a set taper angle during taper cut.

  A wire electrode, which is a tool electrode, is stretched between a pair of wire guides with a predetermined tension applied, and a machining voltage is applied to the machining gap formed between the wire electrode and the workpiece to discharge the wire electrode. A wire-cut electric discharge machining is known in which a wire electrode and a workpiece are moved relative to each other and the workpiece is machined into a desired shape by electric discharge energy. In a general wire cut electric discharge machining apparatus, the wire guides are provided up and down across the workpiece. During electric discharge machining, the wire electrode runs from the direction of one wire guide to the direction of the other wire guide.

  In order to obtain a desired machining shape, it is required to move the wire electrode along a required relative movement locus on an arbitrary plane (hereinafter referred to as a program plane) orthogonal to the plate thickness direction of the workpiece. The relative movement trajectory of the wire electrode is represented by a machining program such as an NC program. The control device decodes the machining program, analyzes the program data (NC data in the case of the NC program), and outputs the movement data to the movement control device. The movement control device controls the positioning of each moving body so that the wire electrode actually moves relative to the workpiece along the required relative movement locus with reference to the program plane.

  The wire guide not only guides the travel of the wire electrode, but also positions the wire electrode relative to the workpiece. The wire guide used in the wire-cut electric discharge machining apparatus can be divided into several types depending on the configuration, material, etc., one of which is a die guide. In recent years, the die guide has an advantage that diamond or sapphire is used for the guide body, wear of the guide body is small, and positioning accuracy can be maintained.

  In many wire guides, a slight gap (hereinafter referred to as clearance) is provided between the wire electrode and the wire electrode so that the wire electrode can be easily inserted into the wire guide and smoothly run. The clearance is a value of about 5 μm to 20 μm, but in wire-cut electric discharge machining requiring machining shape accuracy of several μm or less, an unacceptable position error may occur. When the wire electrode is a thin wire having a diameter of 0.1 mm or less, the clearance of 5 μm to 20 μm cannot be said to be a relatively small value with respect to the diameter of the wire electrode.

  FIG. 5 shows the positional relationship between the wire electrode and the upper wire guide when projected onto an arbitrary XY plane formed by the X axis and the Y axis in the first cut. The first cut indicates an initial machining step in which electric discharge machining is performed so as to cut an unmachined workpiece. At this time, the wire electrode 1 is stretched in a direction perpendicular to an arbitrary XY plane (generally a horizontal plane) (hereinafter simply referred to as a vertical direction) in a state where a predetermined tension is applied. In the case of the first cut, the wire electrode 1 is constrained by the machining groove formed in the workpiece 2, so that, for example, the progress of the wire electrode 1 is caused by the influence of the discharge reaction force and the pressure of the machining liquid jet during machining. It is pushed back in the direction 12 opposite to the direction 11.

  The control device calculates the command value on the assumption that the center position Ow of the wire electrode 1 is at the center position Ou of the guide hole of the upper wire guide 3 and the center position of the guide hole of the lower wire guide (not shown). Therefore, when the upper wire guide 3 or the lower wire guide has a clearance L, an error occurs in the position of the wire electrode 1 by a distance corresponding to the one-side clearance (L / 2), and the machining shape accuracy is lowered. When the pair of upper and lower wire guides 3 and 4 have a clearance, an error occurs in the horizontal position of the wire electrode by a distance corresponding to the one-side clearance in each of the upper and lower wire guides.

  FIG. 6 shows the positional relationship between the wire electrode and the upper wire guide when projected onto an arbitrary XY plane. The second cut indicates an end surface finishing process for finishing the processed surface of the workpiece. At this time, the wire electrode 1 is stretched in a vertical direction in a state where a predetermined tension is applied. Since the wire electrode 1 relatively moves along the processing surface of the workpiece 2, during the processing, the offset direction perpendicular to the traveling direction of the wire electrode due to the influence of the discharge reaction force and the pressure of the processing liquid jet (more precisely, It is pushed slightly backwards. For example, in the case shown in FIG. 5, the wire electrode 1 is pushed back in the opposite direction 14 with respect to the machining surface perpendicular to the traveling direction 13.

  The control device calculates the command value on the assumption that the center position Ow of the wire electrode 1 is at the center position Ou of the guide hole of the upper wire guide 3 and the center position of the guide hole of the lower wire guide (not shown). Therefore, when the upper wire guide 3 or the lower wire guide has a clearance L, an error occurs in the position of the wire electrode 1 by a distance corresponding to the one-side clearance (L / 2), and the machining shape accuracy is lowered. When the pair of upper and lower wire guides 3 and 4 have a clearance, an error occurs in the horizontal position of the wire electrode by a distance corresponding to the clearance on one side of each of the upper and lower wire guides.

  In wire cut electric discharge machining, there is a machining method called taper cutting (taper machining) in which a workpiece is machined by inclining wire electrodes. Even when the wire electrode is inclined, the required relative movement trajectory of the wire electrode in the program plane is the same as when the wire electrode is stretched in the vertical direction. However, in the case of the taper cut, the wire electrode is generally inclined by a method in which the pair of upper and lower wire guides are relatively displaced in the horizontal direction, so that the horizontal direction of the wire guide projected onto an arbitrary XY plane at that time The position of is different from the position of the wire guide when the wire electrode is stretched in the vertical direction. Each coordinate position of the wire guide in the taper cut is, for example, as shown in Patent Document 1 and Patent Document 2, the position coordinate value of the wire electrode on the program plane, the taper angle, and the wire guide to the program plane. It can be obtained from the distance using a trigonometric function.

  FIG. 4 shows a wire electrode stretched between a pair of upper and lower wire guides with a workpiece to be cut in a taper cut. Since the wire electrode 1 is in a state where a predetermined tension is applied, in the case of a taper cut, the wire electrode 1 is pulled in the inclination direction of the wire electrode 1. For example, in the case shown in FIG. 4, the wire electrode 1 is pulled in the inclined directions 15 and 16. In this case, as shown in FIG. 4, the inclination direction 15 viewed from the upper wire guide 3 and the inclination direction 16 viewed from the lower wire guide 4 are reversed. At this time, as shown in FIG. 4, it can be seen that the actual wire electrode inclination angle α becomes smaller than a predetermined taper angle θ.

FIG. 3 shows the positional relationship between the wire electrode and the upper and lower wire guides when projected onto an arbitrary XY plane. Since the control device calculates the command value on the assumption that the center position Ow of the wire electrode 1 is at the center position Ou ₀ , Ob ₀ of each guide hole of the upper and lower wire guides 3, 4, the upper wire guide Accordingly, an error occurs in the horizontal position of the wire electrode 1 in the inclination directions 15 and 16 of the wire electrode 1 by a distance corresponding to the one-side clearance Lu of 3 and the one-side clearance Lb of the lower wire guide 4. For this reason, an error occurs in the position of the wire electrode 1 by a distance corresponding to the one-side clearance Lu of the upper wire guide 3 and the one-side clearance Lb of the lower wire guide 4, and the machining shape accuracy is lowered.

  Thus, the error in the horizontal position of the wire electrode caused by the clearance of the wire guide gives different results depending on the type of processing. In the case of the first cut, when processing that requires the inside as a processed product, such as a punch of a mold, it is processed too much and smaller than the desired processing shape, conversely like a die of a mold When processing the outside as a processed product, the processing is performed to be larger than a desired processing shape. In the case of the second cut, the machining is insufficient and the machining is larger than the desired machining shape. This problem can be improved by moving the position of the wire guide to a position that supports the reaction force received by the wire electrode.

  For example, Patent Document 3 discloses a wire cut discharge that can be rotated so that a contact point with a guide hole is positioned at a position that supports a reaction force received by a wire electrode, thereby preventing vibration of the wire electrode and improving processing accuracy. Processing machines have been proposed. Patent Document 4 discloses a wire that detects a horizontal position of a wire electrode in a guide hole of a wire guide with a detection device and pulls the wire electrode in a direction opposite to the advancing direction to eliminate a machining shape error caused by bending of the wire electrode. A cut electrical discharge machining device has been proposed to prevent a reduction in machining shape accuracy due to bending of the wire electrode. Incidentally, Patent Document 5 discloses that the positioning accuracy of the wire electrode can be obtained only by the clearance or more accuracy due to the clearance of the wire guide.

  However, in the case of taper cut, the error in the position of the wire electrode due to the clearance of the wire guide causes an error in the taper angle. This creates a problem where the desired angle is not achieved. Specifically, for example, there is a problem that the blade thickness dimension is not obtained in the cutting blade processing. Therefore, since correction after machining in taper cutting is almost impossible, it is necessary to ensure sufficient machining accuracy before machining. For this reason, when taper cutting is performed, the error is actually measured by performing test processing in advance, and processing is performed after the numerical value is corrected (see Patent Document 6 and Patent Document 7).

JP 59-81022 A JP 61-30331 A Japanese Utility Model Publication No. 56-67923 (pages 5 to 6) Japanese Examined Patent Publication No. 4-78411 (page 3, Fig. 4) JP 2003-71636 A (pages 3 to 4) JP 2000-24839 A (page 4) JP-A-2-279220 (page 3)

  Thus, when performing taper cutting, some test processing is required, and the setup time tends to be long. It is conceivable that the measured records are accumulated and converted into a database, and an appropriate value of the distance between the wire guides with respect to the set taper angle is read from the data table stored in the storage device, and the taper is cut at the correct taper angle. . However, since it is necessary to prepare measurement data that can sufficiently cope with changes such as the taper angle and the diameter of the wire electrode, a lot of measurement data is required. In addition, when trying to accurately machine a machining shape in which the taper angle gradually changes while moving from one movement position to the next movement position, a large amount of measurement data is required. It is difficult.

  In view of the above problems, the present invention corrects a taper angle error caused by a wire guide clearance in wire-cut electric discharge machining in which a wire electrode is inclined at a predetermined angle to taper-cut a workpiece. It is an object of the present invention to provide a wire cut electric discharge machining method, a wire cut electric discharge machining control method, and a wire cut electric discharge machining apparatus capable of performing taper cutting to reduce a reduction in machining accuracy. Several other advantages of the present invention will be described as they are described with specific embodiments of the present invention.

  In the wire cut electric discharge machining method of the present invention, the wire cut electric discharge is performed by tapering the workpiece 2 by inclining the wire electrode 1 stretched between the pair of wire guides 3 and 4 to a predetermined taper angle. In the processing method, the coordinate position of the wire guide 3 (4) in the horizontal direction is set to the one-side clearance (L / 2) of the wire guide 3 (4) for each interpolation position in numerical control where the inclination direction of the wire electrode 1 is changed. The taper machining is performed by correcting in a direction opposite to the inclination direction by a considerable amount.

  In the wire cut electric discharge machining control method of the present invention, the workpiece 2 is tapered by inclining the wire electrode 1 stretched between the pair of wire guides 3 and 4 to a taper angle set in advance according to a machining program. In the wire cut electric discharge machining method, the machining program is analyzed to obtain the coordinate position of each interpolation position in numerical control, and the coordinate position of the wire guide 3 (4) corresponding to the coordinate position of the wire electrode 1 is obtained. A step of calculating a horizontal distance G between the pair of wire guides 3 and 4 projected on an arbitrary XY plane based on the coordinate position of the wire guide 3 (4), and the coordinates of the wire guide 3 (4) Calculating the correction coordinate position of the wire guide 3 (4) based on the position, the horizontal distance G and the clearance L of the wire guide 3 (4), and based on the correction coordinate position In horizontal direction and a step of correcting the coordinate position of the wire guide 3 (4) in the tilting direction 15 (16) opposite to the direction 17 of the wire electrode 1 (18), the.

  The wire-cut electric discharge machining apparatus according to the present invention includes a pair of moving bodies 48 and 50 for moving the wire electrode 1 and the workpiece 2 relative to each other; Wire guides 3 and 4; moving bodies 56 and 58 for moving the wire guide 3 in the horizontal direction to incline the wire electrode 1 to a preset angle θ; and positioning control of the moving bodies 48, 50, 56 and 58 An input device 100 capable of inputting the data of the clearance L of the wire guide 3 (4) in the wire-cut electric discharge machining device having the movement control device 46, and each interpolation for numerical control by analyzing the machining program Means for obtaining the coordinate position of the position, means for obtaining the coordinate position of the wire guide 3 (4) corresponding to the coordinate position of the wire electrode 1, and the coordinate position of the wire guide 3 (4). Then, a horizontal distance G between the pair of wire guides 3 and 4 is calculated, and the horizontal wire guide 3 (4) is calculated based on the coordinate position of the wire guide 3 (4), the horizontal distance G, and the clearance L. A numerical control device 44 including: a computing device 200 including: a calculating means for calculating the corrected coordinate position; and a means for calculating movement data based on the corrected coordinate position and outputting the movement data to the movement control device 46.

  The wire-cut electric discharge machining apparatus is preferably capable of inputting data on the diameter of the wire electrode 1 used by the input device 100 and the inner diameter of the wire guide 3 (4). Means for calculating the clearance L of the wire guide from the inner diameter of the wire guide. Each means of the arithmetic unit 200 of the wire-cut electric discharge machining apparatus is provided with the reference numerals corresponding to the embodiments of the invention for convenience of explanation.

  In the wire-cut electric discharge machining method of the present invention, at the time of taper cutting, the coordinate position of the wire guide is opposite to the one-side clearance equivalent inclination direction for each interpolation position in numerical control in which the inclination direction of the wire electrode is changed. Since the taper cut is performed by correcting in the horizontal direction, the error due to the clearance of the wire guide is corrected more appropriately. Therefore, the wire electrode can be positioned and guided more precisely with an accuracy equal to or less than the clearance value of the wire guide in accordance with the gradually changing inclination angle of the wire electrode. In addition, the prior measurement work can be reduced, and the burden on the operator is reduced. Further, since a special device such as a detection device or a storage device for storing a large amount of data as a data table is not required, it can be implemented with an existing wire-cut electric discharge machine. Further, since the taper can be cut with an accurate taper angle without changing the distance between the wire guides, the change with respect to the processing environment is small and the reproducibility is high. As a result, there is an effect that it is possible to more easily perform taper cutting with excellent processing accuracy.

  The wire-cut electric discharge machining control method of the present invention calculates the horizontal distance between a pair of wire guides projected on an arbitrary XY plane based on the coordinate position of the wire guide during taper cut, and coordinates of the wire guide Since the correction coordinate position of the wire guide is calculated based on the position, the horizontal distance, and the clearance of the wire guide, the correction coordinate position of the wire guide that corrects the error caused by the clearance of the wire guide can be obtained relatively easily. Can do. Therefore, the wire electrode can be positioned and guided more precisely according to the gradually changing inclination angle of the wire electrode. In addition, the prior measurement work can be reduced, and the burden on the operator is reduced. Further, since a special device such as a detection device or a storage device for storing a large amount of data as a data table is not required, it can be implemented with an existing wire-cut electric discharge machine. Further, since the taper can be cut with an accurate taper angle without changing the distance between the wire guides, the change with respect to the processing environment is small and the reproducibility is high. As a result, there is an effect that it is possible to more easily perform taper cutting with excellent processing accuracy.

  In the wire cut electric discharge machining apparatus of the present invention, the diameter of the wire electrode and the inner diameter of the wire guide that are used in advance are set by the setting device, so that the clearance of the wire guide can be calculated. The arithmetic unit calculates and corrects the coordinate position of the wire guide corresponding to the coordinate position of the wire electrode, the horizontal distance between the pair of wire guides projected on the XY plane, and the clearance of the wire guide. A coordinate position is calculated, and movement data is output to the movement control device based on the corrected coordinate position. Therefore, each movable body can be positioned and controlled so as to correct an error in the horizontal control of the wire guide caused by the clearance of the wire guide.

  Therefore, the wire electrode can be positioned and guided more precisely according to the gradually changing inclination angle of the wire electrode. In addition, the prior measurement work can be reduced, and the burden on the operator is reduced. When the configuration is such that the correction coordinate position of the wire guide is calculated by inputting the wire electrode diameter and the inner diameter of the wire guide, the burden on the operator is further reduced. Further, since a special device such as a detection device or a storage device for storing a large amount of data as a data table is not required, it can be implemented with an existing wire-cut electric discharge machine. Further, since the taper can be cut with an accurate taper angle without changing the distance between the wire guides, the change with respect to the processing environment is small and the reproducibility is high. As a result, there is an effect that it is possible to more easily perform taper cutting with excellent processing accuracy.

  FIG. 1 shows an example of a preferred wire cut electric discharge machining apparatus of the present invention. FIG. 1 schematically shows a schematic configuration of a wire cut electric discharge machining apparatus. A numerical control device having a configuration in which an axial feeder can move at least one of a wire electrode and a workpiece in a horizontal direction and can move at least one of the upper and lower wire guides in a horizontal direction. Basically, the wire cut electric discharge machining apparatus of the present invention can be implemented as long as the wire cut electric discharge machining apparatus is provided.

  The wire electrode 1 of the wire cut electric discharge machine shown in FIG. 1 is pulled out from a wire bobbin 24 set on a reel 22 equipped with a brake 20, passes through a tension roller 26, and reaches a feed roller 30 of an automatic wire connection device 28. . The wire electrode 1 delivered by the delivery roller 30 passes through the upper wire guide 3, the processing site 32, and the lower wire guide 4, and is connected so as to be taken up by the take-up roller 34. The wire electrode 1 taken up by the take-up roller 34 is collected in the bucket 36. Electric power is supplied from the machining power supply 42 to the wire electrode 1 through the electric conductor 38 and the electric conductor 40. A machining voltage supplied from the machining power supply device 42 is applied to a machining gap formed by the wire electrode 1 and the workpiece 2 to generate an electric discharge in the machining gap. The upper wire guide 3 and the lower wire guide 4 are die guides having a clearance between the wire electrode 1.

  The computer numerical control device 44 and the movement control device 46 are control devices that control the relative movement between the wire electrode 1 and the workpiece 2 by controlling each axis feeding device. Each shaft feeder has a moving body and a servo motor. The saddle 48 reciprocates in the Y axis direction (one horizontal axis direction). The table 50 is disposed on the saddle 48 and reciprocates in the X-axis direction orthogonal to the Y-axis direction. The table 56 is attached to a machining head (not shown) and reciprocates in the U-axis direction parallel to the X-axis direction. The table 58 reciprocates in the V-axis direction parallel to the Y-axis direction and orthogonal to the U-axis direction.

  Each moving body is moved by servo motors 52, 54, 60, and 62, respectively. The table 56 and the table 58 move the upper wire guide 3 in the horizontal direction with respect to the lower wire guide 4. As a result, the wire electrode 1 can be inclined. Therefore, the shaft feeding device including the table 56 and the table 58 may be referred to as a taper device. The taper device moves in the same direction as the machining head when the machining head moves in the Z-axis direction (vertical one-axis direction) orthogonal to the X-axis direction and the Y-axis direction. As a result, the upper wire guide 3 can be moved up and down, and the distance between the upper wire guide 3 and the lower wire guide 4 can be adjusted according to the plate thickness of the workpiece 2.

  The computer numerical control device 44 includes an input device 100, an arithmetic device 200, and a storage device 300. The input device 100 includes a keyboard (not shown), a switch, and a disk drive that reads data from a recording medium or records data. The numerical control device 44 includes a display device (not shown). Necessary setting data can be input from the input device 100 by a user or an operator of a manufacturer and stored in the storage device 300 by the arithmetic device 200. The setting data is, for example, the diameter of the wire electrode to be used and the inner diameter of the wire guide. The setting data includes machining program data and machining condition data. The numerical controller 44 decodes the machining program, analyzes the program data, and calculates a plurality of relative coordinate positions of the wire electrode 1 according to a desired machining shape. The numerical controller 44 outputs movement data including position, velocity, acceleration, or time data to the movement controller 46. The movement control device 46 calculates a movement command value from the movement data, outputs a control current to the servo motors 52, 54, 60, 62, and inputs a feedback signal from the detector to control the positioning of the moving body.

  The arithmetic device 200 has means for calculating the clearance of the wire guide from the diameter of the wire electrode 1 and the inner diameters of the wire guides 3 and 4, and means for analyzing the machining program to determine the coordinate position of each interpolation position in numerical control. Means for obtaining the coordinate position of the pair of wire guides 3 and 4 corresponding to the obtained coordinate position of the wire electrode 1 and the X-axis direction and the Y-axis direction are formed based on the coordinate positions of the wire guides 3 and 4. The horizontal distance between the wire guides 3 and 4 projected on an arbitrary XY plane is calculated, and the wire guides 3 and 4 in the horizontal direction are calculated based on the coordinate position of the wire guides 3 and 4, the horizontal distance and the clearance. Means for calculating each correction coordinate position, and means for calculating movement data based on the correction coordinate position and outputting the movement data to the movement control device 46. Specifically, these means are control programs.

  The arithmetic device 200 includes means for decoding the machining program, analyzing the program data, and determining the type of machining based on the analyzed program data. There are three types of processing that the arithmetic device 200 discriminates: a first cut in which the wire electrode is stretched in the vertical direction, a second cut in which the wire electrode is stretched in the vertical direction, and a taper cut. The control program and the calculation result are stored in the storage device 300.

  FIG. 2 shows an outline of a preferred embodiment of the wire cut electric discharge machining method of the present invention. FIG. 3, FIG. 5 and FIG. 6 show the relationship between the relative positions of the wire guide and the wire electrode projected on the XY plane in each processing type. FIG. 4 shows a wire electrode stretched between a pair of upper and lower wire guides with a workpiece to be cut in a taper cut. In the following embodiments, description will be made assuming that the upper and lower wire guides are die guides. Further, the description will be made assuming that the shaft feeding device is a wire-cut electric discharge machining device of the system shown in FIG.

  In wire-cut electric discharge machining, a machining program such as an NC program in which a desired machining shape is programmed is required. Some setting data necessary for wire-cut electric discharge machining is given to a computer numerical control device (hereinafter simply referred to as a control device) by a machining program. Some setting data is given from the input device to the control device by the operator. Or some setting data are previously memorize | stored in the memory | storage device of the control apparatus. However, the wire-cut electric discharge machining method of the present invention does not limit the required setting data setting method.

  Data required by the control device for carrying out the wire-cut electric discharge machining method of the present invention includes the clearance of the wire guide, the distance from the program plane to the upper and lower wire guides (distance between the wire guides), and the wire electrode on the program plane Position data (position coordinate value), taper angle, and offset value. The data does not necessarily have to be given directly to the control device, and may be obtained by calculation from other data. For example, in the embodiment, the clearance of the wire guide is calculated by the inner diameter of the wire guide (the diameter of the guide hole) and the diameter of the wire electrode. The inner diameter of the wire guide is stored in advance in a storage device of the control device. The diameter of the wire electrode and the distance between the wire guides are directly given to the control device by the operator. The position coordinate value of the coordinate position of the wire electrode for each interpolation position in general numerical control on the relative movement locus is calculated by the control device based on the machining program. The taper angle and the offset value are given to the control device by the machining program.

  In the present invention, each interpolation position in numerical control is a start point and an end point of a program block in the case of linear interpolation. In the case of circular interpolation, the starting point and the ending point of the program block are points (intermediate points and dividing points) that connect the straight lines when equally divided into minute straight lines that approximate a circular arc. A known method is adopted as a method of dividing the arc into minute straight lines. Specifically, for example, the minimum drive unit (setting value) in the movement command value for motor control is x, the radius of the arc is R, and the arc is Cos (dθ / 2) = (R−0.5 × x) where the distance of the farthest part from a minute straight line (string) approximating an arc is one half of the minimum drive unit and the division angle is dθ. From / R, a minute straight line is formed so as to have a division angle dθ. The number of arc divisions at this time, in other words, the number of interpolation positions, can be obtained by dividing the angle of the center of the arc by the division angle dθ. A connection point between minute straight lines having a division angle dθ existing on the relative movement locus of the arc is set as each interpolation position. There are many known methods for representing the relative movement trajectory with continuous minute straight lines, and an appropriate method is adopted in consideration of the time for calculation, the burden on the arithmetic unit, the required accuracy, and the like. In this embodiment, for example, also in linear interpolation, a straight line can be divided into minute straight lines based on the minimum drive unit, and each division point on the relative movement locus can be included in the interpolation position.

  The control device calculates the one-side clearance by dividing the value of the clearance of the wire guide obtained by subtracting the diameter of the wire electrode used for processing from the inner diameter of the wire guide by 2 (S1). Further, the control device obtains the coordinate position of each interpolation position in numerical control in consideration of the offset value in the reference program plane from the program data of the machining program in which the locus of the desired machining shape is programmed (S2).

  Next, the control device determines whether it is a taper cut (S3). The taper cut can be determined by decoding the machining program and analyzing whether the taper angle is set before the program block. In the case of taper cut, each wire guide coordinate position is corrected in the horizontal direction corresponding to the clearance on one side of the wire guide in the direction opposite to the tilt direction for each interpolation position for numerical control where the tilt direction of the wire electrode is changed. (S5 to S8).

  The control device obtains the horizontal coordinate position of the upper and lower wire guides corresponding to the coordinate position of each interpolation position in numerical control on the program plane (S4). As shown in FIG. 4, the horizontal coordinate positions of the upper and lower wire guides in the taper cut are the position coordinate value (x, y) of the wire electrode at the interpolation position and each from the program plane to the upper and lower wire guides. The distances TU and TL and the taper angle θ data can be obtained by a known calculation method using a trigonometric function. When the offset value is set, the horizontal coordinate position of the wire guide is calculated in consideration of the offset value.

Next, as shown in FIG. 3, the control device determines the wire electrode from the position coordinate value of each horizontal coordinate position when the calculated coordinate position of the upper and lower wire guides is projected onto the same arbitrary XY plane. The horizontal distance G between the pair of upper and lower wire guides projected on the XY plane in the inclination direction is calculated (S5). For example, as shown in FIG. 3, the guide hole center position Ou ₀ (xu ₀ , yu ₀ ) of the upper wire guide 3 and the guide hole center position Ob ₀ (xb ₀ , yb ₀ ) of the lower wire guide 4. , The intersection of a line extending point Ou ₀ parallel to the Y axis and a line extending point Ob ₀ parallel to the X axis is set as P, and the distance between point P and point Ob ₀ is it can be calculated from the distance between the points P and Ou _0.

Next, the correction coordinate positions of the pair of upper and lower wire guides are obtained based on the coordinate position of the wire guide, the horizontal distance between the pair of wire guides, and the one-side clearance (S6). In the case of the wire guide shown in FIG. 3, the upper wire guide 3 is a wire guide having a one-side clearance Lu and the lower wire guide 4 is a wire guide having a one-side clearance Lb. The horizontal position coordinate values (xu ₁ , yu ₁ ) and (xb ₁ , yb ₁ ) are calculated by obtaining a deviation vector.

Specifically, for example, the upper wire guide 3 has a center position Ou ₀ (xu ₀ , yu ₀ ) of the upper wire guide, a horizontal distance G between a pair of upper and lower wire guides, and a one-side clearance Lu. Therefore, the position coordinate value of the correction position coordinate of the upper wire guide 3 in the horizontal direction is calculated from the ratio of the vectors: xu ₁ = xu ₀ + Lu · (xu ₀ −xb ₀ ) / G, yu ₁ = yu ₀ + Lu · (yu ₀₋ yb ₀ ) / G. The lower wire guide 4 has a center position Ob ₀ (xb ₀ , yu ₀ ) of the lower wire guide, a horizontal distance G between the pair of upper and lower wire guides, and a one-side clearance Lu. Therefore, the position coordinate value of the correction position coordinate of the lower wire guide 4 in the horizontal direction is calculated from the ratio of vectors: xb ₁ = xb ₀ + Lb · (xb ₀ −xu ₀ ) / G, yb ₁ = yb ₀ + Lb · ( obtained by the yb ₀ -yu ₀₎ / G.

  In the embodiment, even when processing is performed with the wire electrode stretched in the vertical direction, the position of the wire guide can be corrected based on the clearance according to the operator's request. Specifically, when the operator makes a setting for correction by a machining program or a switch, a value is taken in the flag data. When the control device detects the flag data, the position of the wire guide is corrected (S9). When correcting the position of the wire guide in the horizontal direction at times other than the taper cut, it is further determined whether it is a first cut or a second cut (end surface finishing process) (S10).

In the case of the first cut, the coordinate position of the wire guide is corrected in the horizontal direction by an amount equivalent to the one-side clearance L of the wire guide for each interpolation position where the traveling direction of the wire electrode is changed (S11). For example, when the upper wire guide 3 has the one-side clearance Lu and the lower wire guide 4 has the one-side clearance Lb as shown in FIG. 3, the upper wire guide is used in the first cut as shown in FIG. Coordinate positions are corrected in the guide 3 corresponding to the one-side clearance Lu, the lower wire guide 4 in the one-side clearance equivalent Lb, and the wire electrode traveling direction 11 respectively. For example, when the upper wire guide 3 is used as the position coordinate value, the moving position coordinate value is (xu ₁ , yu ₁ ), the start point (xu ₀ , yu ₀ ), the end point (xu ₁ , yu ₁ ), and the length Lu. It can be obtained by the vector.

  For other than the first cut, the wire guide coordinate position is set in the direction of the workpiece surface (anti-offset direction) perpendicular to the direction of travel for each interpolation position where the direction of travel of the wire electrode is changed. The one side clearance equivalent amount is corrected in the horizontal direction (S12). For example, as shown in FIG. 5, when the upper wire guide 3 has a one-side clearance Lu and the lower wire guide 4 has a one-side clearance Lb, the upper wire guide 3 is cut in the second cut as shown in FIG. The coordinate positions are corrected in the guide 3 corresponding to the one-side clearance Lu, the lower wire guide 4 corresponding to the one-side clearance equivalent Lb, and the processing surface direction 19 perpendicular to the traveling direction 13 of the wire electrode. The position coordinate value can be obtained basically in the same manner as in the first cut.

  Based on the positions of the upper and lower wire guides in consideration of the wire guide correction amount calculated in the above process, the actual movement data of the axis feeding device for each axis is calculated (S7). The calculation of the movement data depends on the configuration of the shaft feeding device of the wire cut electric discharge machining apparatus, and is the same as the known calculation method in the taper cut, and thus the detailed calculation process is omitted. In the case of the wire-cut electric discharge machining apparatus of the embodiment shown in FIG. 1, the workpiece 2 is moved in the X-axis direction and the Y-axis direction, and the upper wire guide 3 is moved in the U-axis and V-axis directions. Therefore, the movement data is output in terms of the movement amount of the X axis, Y axis, U axis, and V axis. If the clearance between the upper and lower wire guides is the same value unless the taper is cut, the upper and lower wire guides are corrected in the same amount in the same direction in calculation, and the wire electrode angle changes substantially. Since it is not stretched and remains vertically stretched, the U-axis and V-axis axis feeding devices do not actually operate.

  The process of calculating the correction coordinate position of the wire guide is executed for each interpolation position in numerical control in the relative movement trajectory of the wire electrode on the program plane calculated in step S2 (S8). Therefore, even when the taper angle gradually changes, the correction coordinate position of the wire guide can be calculated for each interpolation position, and the wire electrode can be positioned at the correct position assumed for control. As a result, since the inclination angle of the wire electrode is maintained more accurately with respect to the set taper angle, it is possible to perform machining with excellent machining shape accuracy. In addition, it is not necessary to collect a huge amount of data and create a database.

  The embodiment has been described for the case where a pair of upper and lower wire guides uses a die guide, but the case where a wire guide having a clearance only in one of the upper wire guide and the lower wire guide is used. Even in such a case, the correction coordinate position and the movement data can be calculated in the same manner by setting the correction value of the wire guide having no clearance to zero.

  The present invention is applied to wire-cut electric discharge machining provided with a taper device capable of tilting a wire electrode. The wire-cut electric discharge machining method and the wire-cut electric discharge machining apparatus of the present invention can be used when performing taper cut, and can taper cut with a precise taper angle of the wire electrode. In the present invention, each moving body can be positioned and controlled so as to correct a horizontal control error of the wire guide caused by the clearance of the wire guide, and wire-cut electric discharge machining with excellent machining shape accuracy can be performed more easily. realizable. The present invention can be implemented in combination with a method of correcting the position of the wire guide from another viewpoint, for example, a method of correcting an error due to the bending point of the wire.

It is a side view which shows typically the outline of embodiment of the wire cut discharge apparatus of this invention. It is a flowchart which shows the process of preferable embodiment of the wire cut electric discharge machining method of this invention. It is a top view which shows typically the relative positional relationship of the upper and lower wire guides and wire electrode which were projected on the arbitrary XY planes at the time of taper cut. It is a side view which shows typically the error of the taper angle between a pair of upper and lower wire guides at the time of taper cut. It is a top view which shows typically the relative positional relationship of the upper and lower wire guide and the wire electrode which were projected on the arbitrary XY planes at the time of a first cut. It is a top view which shows typically the relative positional relationship of the up-and-down wire guide and wire electrode which were projected on the arbitrary XY planes at the time of a second cut.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wire electrode 2 Work piece 3 Upper wire guide 4 Lower wire guide 44 Numerical control device 46 Movement control device 48, 50, 56, 58 Moving body 52, 54, 60, 61 Servo motor 100 Input device 200 Arithmetic device 300 Memory apparatus

Claims (4)

  In a wire-cut electric discharge machining method in which a wire electrode stretched between a pair of wire guides is inclined at a preset taper angle to taper a workpiece, numerical control for changing the inclination direction of the wire electrode A wire-cut electric discharge machining method, wherein a taper machining is performed by correcting the coordinate position of the wire guide in the horizontal direction for each interpolation position in a direction opposite to the inclination direction by an amount equivalent to one-side clearance of the wire guide.   In a wire cut electric discharge machining control method for tapering a workpiece by inclining a wire electrode stretched between a pair of wire guides to a taper angle set in advance according to a machining program, the machining program is analyzed and the machining is performed Based on the coordinate position of the wire guide, the step of obtaining the coordinate position of each interpolation position on the numerical control programmed in the program, the step of obtaining the coordinate position of the wire guide corresponding to the coordinate position of the wire electrode A correction coordinate of the wire guide based on a step of calculating a horizontal distance between the pair of wire guides projected on a plane, a coordinate position of the wire guide, a distance in the horizontal direction, and a clearance of the wire guide A step of calculating a position; and a seat of the wire guide in a horizontal direction based on the corrected coordinate position. Wire-cut electric discharge machining control method comprising a step of correcting position in a direction opposite to the inclination direction of the wire electrode.   A moving body that moves the wire electrode and the workpiece relative to each other, a pair of wire guides that are positioned between the workpiece and guide the wire electrode, and the wire guide is moved in the horizontal direction to set the wire electrode in advance. An input device capable of inputting wire guide clearance data in a wire cut electric discharge machining apparatus having a movable body that is inclined at an angle and a movement control device that controls the positioning of each movable body; Means for analyzing and calculating the coordinate position of each interpolation position in numerical control; means for determining the coordinate position of the wire guide corresponding to the coordinate position of the wire electrode; and on the XY plane based on the coordinate position of the wire guide. The horizontal distance between a pair of projected wire guides is calculated, and the coordinate position of the wire guide, the horizontal distance, An arithmetic unit comprising: means for calculating a correction coordinate position of the wire guide in the horizontal direction based on the balance; and means for calculating movement data based on the correction coordinate position and outputting the movement data to the movement control device; A wire-cut electric discharge machining apparatus including a numerical control device.   Data of the diameter of the wire electrode and the inner diameter of the wire guide used by the input device can be input, and the arithmetic unit calculates the clearance of the wire guide from the diameter of the wire electrode and the inner diameter of the wire guide The wire cut electric discharge machining apparatus according to claim 3, comprising:

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