CN109041572B

CN109041572B - Wire electric discharge machine and wire electric discharge machining method

Info

Publication number: CN109041572B
Application number: CN201780003444.2A
Authority: CN
Inventors: 糸数笃; 原正行
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-04-11
Filing date: 2017-04-11
Publication date: 2020-04-07
Anticipated expiration: 2037-04-11
Also published as: DE112017000086T5; WO2018189806A1; JP6266192B1; JPWO2018189806A1; DE112017000086B4; CN109041572A

Abstract

A wire electric discharge machine that generates electric discharge between a workpiece and a wire electrode to machine the workpiece, the wire electric discharge machine comprising: a drive control device (20) for controlling the relative distance between the wire electrode and the workpiece; an average machining voltage detection unit (40) between the wire electrode and the workpiece, which detects the average machining voltage between the wire electrode and the workpiece; a machining speed control unit (43) that controls the drive control device on the basis of the inter-electrode average machining voltage and a preset target voltage; and a voltage correction unit that corrects either the average machining voltage between the electrodes or the target voltage so that the side gap between the wire electrode and the workpiece is constant regardless of the machining direction, based on the machining information and the machining direction during machining.

Description

Wire electric discharge machine and wire electric discharge machining method

Technical Field

The present invention relates to a wire electric discharge machine and a wire electric discharge machining method for machining a workpiece by wire electric discharge.

Background

As a method for improving machining accuracy in wire electric discharge machining, as disclosed in patent document 1, there is proposed a technique for detecting a machining state during machining and correcting at least one of a set voltage and an average machining voltage between electrodes so that a side gap between a wire electrode and a workpiece becomes constant, in accordance with the machining state. This improves the machining accuracy based on the machining state.

In addition, in the wire electric discharge machine, in order to improve the feeding of the wire electrode, a feeding member electrically connected to a machining power supply is pressed against the wire electrode to perform machining. In wire electric discharge machining, electric discharge occurs on the side surface of the wire electrode facing the workpiece, but the wire electrode wears down as the electric discharge progresses, and therefore, if the electric discharge machining is performed in a direction in which the feeding member is pressed, the position of the center of the electrode deviates. If finishing is performed in a state where a positional deviation of the electrode center is generated, the finishing size fluctuates, and therefore the finishing size fluctuates according to the machining direction.

Patent document 1: japanese patent No. 5794401

Disclosure of Invention

In recent years, high machining accuracy is required for wire electric discharge machines, and countermeasures are being taken against the fluctuation of the finish dimension depending on the machining direction as described above, but the technique disclosed in patent document 1 does not perform correction depending on the machining direction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a wire electric discharge machine capable of suppressing fluctuation of a machining dimension error depending on a machining direction.

In order to solve the above problems and achieve the object, the present invention is a wire electric discharge machine that generates electric discharge between a workpiece and a wire electrode to machine the workpiece, the wire electric discharge machine including: a drive control device for controlling the relative distance between the wire electrode and the workpiece; and an average machining voltage detection unit between the wire electrode and the workpiece, which detects an average machining voltage between the wire electrode and the workpiece. The present invention is characterized by further comprising: a machining speed control unit that controls the drive control device based on the inter-electrode average machining voltage and a preset target voltage; and a voltage correction unit that corrects either the average machining voltage or the target voltage between the electrodes so that the side gap between the wire electrode and the workpiece is constant regardless of the machining direction, based on the machining information and the machining direction during machining

ADVANTAGEOUS EFFECTS OF INVENTION

The wire electric discharge machine according to the present invention achieves an effect of suppressing fluctuation of a machining dimension error depending on a machining direction.

Drawings

Fig. 1 is a configuration diagram of a wire electric discharge machine according to embodiments 1 to 4 of the present invention.

Fig. 2 is a diagram illustrating a shape of the wire electrode in a plane perpendicular to the stretching direction in non-machining according to embodiment 1.

Fig. 3 is a diagram illustrating a shape of the wire electrode in the finish machining in a plane perpendicular to the stretching direction according to embodiment 1.

Fig. 4 is a diagram for explaining another shape of the wire electrode in the finish machining in the plane perpendicular to the stretching direction according to embodiment 1.

Fig. 5 is a diagram showing a relationship between a wire electrode and a workpiece at the time of finishing according to embodiment 1.

Fig. 6 is a diagram showing a machining dimension error depending on the machining direction according to embodiment 1.

Fig. 7 is a diagram showing a detailed configuration of the machining control device according to embodiment 1.

Fig. 8 is a block diagram showing a more detailed configuration of the machining control device according to embodiment 1.

Fig. 9 is a diagram showing a hardware configuration of the cnc control apparatus according to embodiment 1.

Fig. 10 is a diagram showing a relationship between a side gap correction value and a change amount of a machining dimension in the wire electric discharge machine according to embodiment 1.

Fig. 11 is a diagram showing a detailed configuration of a machining control device according to embodiment 2 of the present invention.

Fig. 12 is a block diagram showing a more detailed configuration of the machining control device according to embodiment 2.

Detailed Description

Next, a wire electric discharge machine and a wire electric discharge machining method according to embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the present embodiment.

Embodiment 1.

Fig. 1 is a configuration diagram of a wire electric discharge machine 100 according to embodiment 1 of the present invention. The wire electric discharge machine 100 includes: a wire electrode 30; an upper power feeder 31 and a lower power feeder 32 which are in contact with the wire electrode 30; a processing power supply 35; and a table 9 for mounting a workpiece 13. The upper feeder 31 and the lower feeder 32 are pressed against the upper pressing block 33 and the lower pressing block 34 via the wire electrode 30 in order to satisfactorily maintain the feeding of the wire electrode 30.

Further, the wire electric discharge machine 100 includes: a drive control device 20 including an X-axis drive device 7 and a Y-axis drive device 8; and an upper wire guide nozzle 1 and a lower wire guide nozzle 2 through which the wire electrode 30 is passed, respectively. The X-axis drive 7 moves the table 9 in the X-axis direction, and the Y-axis drive 8 moves the table 9 in the Y-axis direction. Here, the X-axis direction and the Y-axis direction are 2 directions perpendicular to each other in a plane perpendicular to the vertical direction in fig. 1, that is, the extending direction of the wire electrode 30. In the following, the machining direction is described as an in-plane direction including the X-axis direction and the Y-axis direction as an example, but the machining direction is not limited to the in-plane direction perpendicular to the stretching direction of the wire electrode 30.

The upper wire guide 1 has a hole for guiding the wire electrode 30, and positions the wire electrode 30 above the workpiece 13. The lower wire guide 2 has a hole for guiding the wire electrode 30, and positions the wire electrode 30 below the workpiece 13. When the wire electrode 30 is tilted, the upper wire guide 1 and the lower wire guide 2 serve as upper and lower support points of the wire electrode 30.

The drive control device 20 moves any or all of the table 9 on which the workpiece 13 is mounted, the upper yarn guide 1, and the lower yarn guide 2. The drive control device 20 may be a drive system that controls the relative distance between the wire electrode 30 and the workpiece 13. Here, as an example, the X-axis drive device 7 and the Y-axis drive device 8 move the table 9. When the X-axis drive unit 7 and the Y-axis drive unit 8 drive the table 9, the positions of the upper godet 1 and the lower godet 2 are moved relative to the workpiece 13 on the XY plane.

Further, the wire electric discharge machine 100 includes: a bobbin 3 for supplying a line electrode 30; a feed roller 4 that changes the traveling direction of the wire electrode 30 and sandwiches the wire electrode 30; a lower roller 5 for changing the traveling direction of the wire electrode 30; and a collection roller 6 that collects the wire electrode 30 whose direction is changed by the lower roller 5.

Further, the wire electric discharge machine 100 includes: a processing power supply 35; a processing control device 111 that controls the drive control device 20; and a data input/output device 120 serving as an input/output means for an operator. The upper power feeder 31, the lower power feeder 32, and the workpiece 13 are connected to a machining power source 35, respectively. The machining power source 35 applies a voltage between the upper power feeding unit 31 and the lower power feeding unit 32 and the workpiece 13. The wire electric discharge machine 100 performs electric discharge machining on the workpiece 13 by generating electric discharge between the workpiece 13 mounted on the table 9 and the wire electrode 30.

The operator inputs machining conditions, machining programs, and control parameters to the data input/output device 120. The machining controller 111 controls the drive controller 20 based on the machining conditions, the machining program, and the control parameters input by the operator via the data input/output device 120. That is, the machining Control device 111 and the data input/output device 120 constitute a Computer Numerical Control (CNC) device.

In the wire electric discharge machine 100 configured as described above, the wire electrode 30 is fed from the wire bobbin 3 and is changed in direction by the supply roller 4. Then, the wire electrode 30 passes through the hole of the upper wire guide 1 and the hole of the lower wire guide 2, and performs electric discharge machining on the workpiece 13 while passing between the upper wire guide 1 and the lower wire guide 2. The wire electrode 30 passes through the lower godet 2, is changed in direction by the lower roller 5, and is collected by the collection roller 6 into a collection box, not shown.

Fig. 2 is a diagram illustrating a shape of the wire electrode 30 in a plane perpendicular to the stretching direction in non-machining according to embodiment 1. Fig. 3 is a diagram illustrating a shape of the wire electrode 30 in the finish machining in a plane perpendicular to the stretching direction according to embodiment 1. Fig. 4 is a diagram for explaining another shape of the wire electrode 30 in the finish machining in the plane perpendicular to the stretching direction according to embodiment 1. Fig. 5 is a diagram showing a relationship between the wire electrode 30 and the workpiece 13 during the finish machining according to embodiment 1.

Fig. 2 to 4 are diagrams showing the arrangement relationship of the wire electrode 30, the lower wire guide nozzle 2, the lower power feeder 32, and the lower pressing block 34 when viewed from the table 9 in the direction in which the wire electrode 30 is stretched. Fig. 2 shows a non-machining state, fig. 3 shows a state in which discharge machining is performed on the surface of the wire electrode 30 in contact with the lower pressing block 34, and fig. 4 shows a state in which discharge machining is performed on the surface of the wire electrode 30 in contact with the lower feeder 32. Fig. 5 shows a front gap and a side gap between the wire electrode 30 and the workpiece 13. The side gap is a distance between the wire electrode 30 and the workpiece 13 in a direction perpendicular to the machining direction.

As shown in fig. 2, the shape of the wire electrode 30 during non-machining is substantially circular, and the center of the wire electrode 30 is a position controlled by the machining controller 111 as the center position of the wire electrode 30. In contrast, in fig. 3 and 4, due to the consumption of the wire electrode 30 during the finish machining, the actual center of the wire electrode 30 is deviated from the position controlled by the machining control device 111 as the center position of the wire electrode 30 in the 1-piece shape machining depending on the machining direction in which the finish machining is performed. As a result, a deviation occurs in the control of the side gap, and thus a problem occurs in that the shape and the size fluctuate depending on the machining direction.

Fig. 6 is a diagram showing a machining dimension error depending on the machining direction according to embodiment 1. The distance 51 from the origin point of the point 50 indicating the machining dimension error with respect to the machining direction θ when the positive direction of the X axis is 0 degrees and the positive direction of the Y axis is 90 degrees shows the value of the machining dimension error. A case where the machining direction θ is 45 degrees will be described as an example, and when the distance 51 is the direction of 45 degrees in fig. 6 as the machining direction in fig. 5, a machining dimension error, which is an error of a machining dimension in a direction perpendicular to the machining direction with respect to a design value, is shown by the distance 51. If the value of the distance 51 indicating that the machining dimension error is zero is set, the larger the magnitude of the distance 51 is, the more machining remains on the workpiece 13 than the design value is, the smaller the magnitude of the distance 51 is, and the deeper the cutting is performed on the workpiece 13 than the design value is.

Therefore, as shown in fig. 6, it is found that the machining dimension error is not constant regardless of the machining direction. As described above, one of the reasons why the machining dimension error of the finish machining varies depending on the machining direction is that the center of the wire electrode 30 varies depending on the machining direction due to wear of the wire electrode 30 during the finish machining described with reference to fig. 3 and 4. Here, from the viewpoint of machining control, it is desirable that the machining dimension error be constant regardless of the machining direction. That is, it is desirable that the dots 50 of FIG. 6 be arranged on concentric circles.

Fig. 7 is a diagram showing a detailed configuration of the machining controller 111 according to embodiment 1. In fig. 7, in order to explain the configuration of the machining control device 111 in detail, other configurations such as the wire electrode 30, the workpiece 13, and the machining power source 35 are shown in a simplified manner.

The machining controller 111 controls the machining speed via the drive controller 20 based on the machining program and the machining-gap average machining voltage between the wire electrode 30 and the workpiece 13. The machining speed is a relative speed between the wire electrode 30 and the workpiece 13.

The machining control device 111 includes: an inter-electrode average machining voltage detection unit 40 that detects an inter-electrode average machining voltage; a side clearance estimator 45 that estimates a side clearance during machining and outputs the estimated side clearance as a side clearance estimated value; a side gap commander 46 that outputs a side gap command value based on the machining direction; and a side gap controller 47 that generates and outputs a correction value of the inter-electrode average machining voltage so that the side gap estimation value follows the side gap command value.

The machining control device 111 further includes: a machining-gap average machining voltage correction unit 41 that corrects the machining-gap average machining voltage detected by the machining-gap average machining voltage detection unit 40 by a correction value; a target voltage storage unit 44 that stores a target voltage set in advance for machining at a target machining-gap average machining voltage; a voltage calculation unit 42 that calculates a voltage difference between the corrected inter-electrode average machining voltage and a target voltage; and a machining speed control unit 43 that controls the machining speed via the drive control device 20 so as to reduce the absolute value of the voltage difference obtained by the voltage calculation unit 42. The inter-electrode average machining voltage correction unit 41, the side gap estimator 45, the side gap commander 46, and the side gap controller 47 constitute a voltage correction unit that corrects the inter-electrode average machining voltage.

The side clearance estimator 45 estimates the distance between the machined side surfaces from the machining information during the finish machining, and outputs the estimated side clearance value. The machining information includes information such as an average machining voltage between electrodes, a machining speed, a plate thickness, and an offset amount. A method of estimating the side gap is known, and fig. 6 and the like in patent document 1 describe a case where the side gap is determined based on the machining-gap average machining voltage and the machining speed. In embodiment 1, the side gap estimator 45 is configured to obtain and output a side gap estimation value based on the average machining voltage between electrodes detected by the average machining voltage between electrodes detection unit 40 and the machining speed obtained from the machining speed control unit 43, as an example.

The side gap commander 46 has a side gap correction value corresponding to the machining direction. The side gap correction value corresponding to the machining direction is a correction value for the side gap determined for each machining direction so that the machining dimension error obtained from the experimental data shown in fig. 6 becomes a constant value regardless of the machining direction. Specifically, the side gap correction value is a correction value obtained so that the side gap is constant regardless of the machining direction. The side clearance correction value corresponding to the machining direction may be calculated in advance and given to the side clearance commander 46 by the operator via the data input/output device 120. Further, the operator may give data of the machining dimension error depending on the machining direction as shown in fig. 6 to the side clearance commander 46 via the data input/output device 120, and the side clearance commander 46 may calculate and hold the side clearance correction value corresponding to the machining direction based on the machining dimension error depending on the machining direction. The side gap correction value corresponding to the machining direction is a finite number of data corresponding to a finite number of machining directions. The side clearance commander 46 also has a side clearance command value before correction as a fixed value independent of the machine direction. The side clearance commander 46 acquires the machining direction from the drive control device 20, and adds the side clearance correction value corresponding to the machining direction and the side clearance command value before correction to obtain and output a corrected side clearance command value. Therefore, the side clearance command value is corrected in the above-described limited number of machining directions.

The side gap controller 47 obtains and outputs a correction value of the inter-electrode average machining voltage so that the side gap estimated value follows the side gap command value output by the side gap command 46. Here, the side gap controller 47 may have a proportional characteristic in which a deviation between the side gap command value and the side gap estimated value is input as an input/output characteristic and a correction value of the inter-electrode average machining voltage is output as an input/output characteristic, or may have an integral characteristic or a differential characteristic as in a normal servo system. The side gap controller 47 may have a nonlinear input/output characteristic. The side gap controller 47 is not limited as long as it outputs the correction value of the inter-electrode average machining voltage so as to follow the side gap estimated value to the side gap command value.

Fig. 8 is a block diagram showing a more detailed configuration of the machining controller 111 according to embodiment 1.

In fig. 8, the side clearance commander 46 obtains and outputs the side clearance command value corrected by the side clearance correction value as described above based on the machining direction given by the drive control device 20, which is not shown in fig. 8. The side gap estimator 45 obtains and outputs a side gap estimation value based on the machining speed obtained from the machining speed controller 43 and the machining voltage detected by the machining-gap average machining voltage detector 40, which is not shown in fig. 8. In fig. 8, a part of the function of the side clearance controller 47 of fig. 7 is shown outside the side clearance controller 47 as a subtractor 49. The subtractor 49 calculates a deviation between the side clearance command value and the side clearance estimated value, and inputs the deviation to the side clearance controller 47. The side gap controller 47 obtains a correction value of the inter-electrode average machining voltage based on the deviation obtained by the subtractor 49 and outputs the correction value. The subtractor 49 may also have a function provided by the side gap controller 47 as shown in fig. 7. The machining-gap average machining voltage correcting unit 41 is an adder that adds the machining-gap average machining voltage detected by the machining-gap average machining voltage detecting unit 40 to a correction value of the machining-gap average machining voltage output from the side gap controller 47, and outputs the corrected machining-gap average machining voltage. The voltage calculation unit 42 is a subtractor that calculates a voltage difference between the target voltage obtained from the target voltage storage unit 44, which is not shown in fig. 8, and the corrected inter-electrode average machining voltage, and inputs the voltage difference to the machining speed control unit 43. The machining speed controller 43 obtains a machining speed at which the absolute value of the input voltage difference decreases, and supplies the machining speed to the drive controller 20. The drive control device 20 controls the relative distance between the wire electrode 30 and the workpiece 13 so as to achieve the machining speed. Therefore, the voltage correction unit including the inter-electrode average machining voltage correction unit 41 corrects the inter-electrode average machining voltage so that the side gap is constant regardless of the machining direction. That is, according to the wire electric discharge machine 100 according to embodiment 1, it is possible to control the side surface gap in the case where machining is performed in one linear direction to have the same value as the side surface gap in the case where machining is performed in the other linear direction by changing the angle between the side surface gap and the machining direction.

Fig. 9 is a diagram showing a hardware configuration of the cnc control apparatus according to embodiment 1. When the functions of the machining control device 111 and the data input/output device 120 are implemented by a computer, the functions of the machining control device 111 and the data input/output device 120 are implemented by a cpu (central Processing unit)201, a memory 202, a storage device 203, a display device 204, and an input device 205, as shown in fig. 9.

The functions of the process control apparatus 111 are implemented by software, firmware, or a combination of software and firmware. The software, firmware, or a combination of the software and firmware is stored as a program description in the storage device 203. The CPU 201 reads out the program stored in the storage device 203 to the memory 202 and executes the program, thereby executing the function of the machining controller 111. That is, when the computer executes the function of the machining controller 111 by a computer, the cnc device includes a storage device 203, and the storage device 203 stores the program that is executed as a result of the steps that implement the function of the machining controller 111. The program may cause a computer to execute a wire electric discharge machining method that realizes the function of the machining controller 111. Therefore, the program also includes the machining program. The data input/output device 120 is implemented by an input device 205 and a display device 204. Specific examples of the input device 205 include a keyboard, a mouse, and a touch panel. Specific examples of the display device 204 include a monitor and a display. The target voltage storage unit 44 is realized by the memory 202 or the storage device 203. A specific example of the memory 202 corresponds to a volatile memory area such as a ram (random Access memory). A specific example of the storage device 203 corresponds to a nonvolatile or volatile semiconductor memory or a magnetic disk.

Fig. 10 is a diagram showing a relationship between the side gap correction value and the amount of change in the machining dimension in the wire electric discharge machine 100 according to embodiment 1. Fig. 10 shows the amount of change in the machining dimension with respect to the used side gap correction value when a steel material having a thickness of 60mm is machined by the wire electric discharge machine 100. The amount of change in the machining dimension linearly changes with respect to the side gap correction value. Therefore, the effectiveness of controlling the side gap is shown in the side gap command value corrected by the side gap correction value by the wire electric discharge machine 100.

That is, according to the wire electric discharge machine 100 according to embodiment 1, the machined dimension can be controlled by changing the finished side clearance using the side clearance correction value corresponding to the machining direction. This can suppress variation in machining dimension error depending on the machining direction, which varies depending on the machining shape and material of each workpiece 13. As a result, the processing conditions can be easily adjusted.

Embodiment 2.

The configuration of the wire electric discharge machine 100 according to embodiment 2 of the present invention is the same as that of fig. 1 except that the machining controller 111 is changed to a machining controller 112 described below. In the wire electric discharge machine 100 according to embodiment 2, the target voltage is corrected instead of the inter-electrode average machining voltage. The hardware configuration of the cnc control apparatus including the processing control apparatus 112 and the data input/output apparatus 120 is also the same as that of fig. 9.

Fig. 11 is a diagram showing a detailed configuration of the machining control device 112 according to embodiment 2 of the present invention. In fig. 11, in order to explain the configuration of the machining control device 112 in detail, other configurations such as the wire electrode 30, the workpiece 13, and the machining power source 35 are shown in a simplified manner. In the following, descriptions of the same points as those of the machining control device 111 according to embodiment 1 will be omitted, and descriptions of different points will be provided.

The side gap controller 47 obtains and outputs a correction value of the target voltage so that the side gap estimated value follows the side gap command value output by the side gap command 46. A specific example of the correction value of the target voltage is a value obtained by inverting the reference numeral of the correction value of the inter-electrode average machining voltage in embodiment 1. Here, the side gap controller 47 may have a proportional characteristic in which a deviation between the side gap command value and the side gap estimated value is input as an input/output characteristic and a correction value of the target voltage is output, or may have an integral characteristic or a differential characteristic as in a normal servo system. The side gap controller 47 may have a nonlinear input/output characteristic. The side gap controller 47 is not limited in its configuration as long as it outputs the correction value of the target voltage so as to follow the side gap estimated value to the side gap command value.

The target voltage correcting unit 48 corrects the target voltage output from the target voltage storage unit 44 using the correction value of the target voltage obtained from the side gap controller 47. The voltage calculation unit 42 calculates a voltage difference between the average machining voltage between the machining electrodes detected by the average machining voltage between the machining electrodes detection unit 40 and the corrected target voltage obtained from the target voltage correction unit 48. The target voltage correction unit 48, the side gap estimator 45, the side gap commander 46, and the side gap controller 47 constitute a voltage correction unit that corrects the target voltage.

Fig. 12 is a block diagram showing a more detailed configuration of the machining control device 112 according to embodiment 2. In the following, descriptions of the same points as those of the machining control device 111 according to embodiment 1 will be omitted, and descriptions of different points will be given.

In fig. 12, a part of the function of the side clearance controller 47 of fig. 11 is also shown outside the side clearance controller 47 as a subtractor 49. The side gap controller 47 obtains a correction value of the target voltage based on the deviation obtained by the subtractor 49 and outputs the correction value. The subtractor 49 may also have a function provided by the side gap controller 47 as shown in fig. 11. The target voltage correction unit 48 is an adder that adds a target voltage obtained from the target voltage storage unit 44, which is not shown in fig. 12, to a correction value of the target voltage output from the side gap controller 47, and outputs the corrected target voltage. The voltage calculation unit 42 is a subtractor that calculates a voltage difference between the corrected target voltage and the average machining voltage between the machining gap detected by the average machining voltage between the machining gaps detection unit 40, which is not shown in fig. 12, and inputs the voltage difference to the machining speed control unit 43. The machining speed controller 43 obtains a machining speed at which the absolute value of the input voltage difference decreases, and supplies the machining speed to the drive controller 20. The drive control device 20 controls the relative distance between the wire electrode 30 and the workpiece 13 so as to achieve the machining speed. Therefore, the voltage correction unit including the target voltage correction unit 48 corrects the target voltage so that the side gap is constant regardless of the machine direction. That is, in the wire electric discharge machine 100 according to embodiment 2, it is also possible to control the side surface gap to have the same value when the angle between the side surface gap and the machining direction is changed when machining is performed in a certain linear direction and when machining is performed in another linear direction.

According to the wire electric discharge machine 100 according to embodiment 2, the same effects as those of embodiment 1 can be obtained by correcting the target voltage instead of correcting the inter-electrode average machining voltage.

Embodiment 3.

In

embodiments

1 and 2, the side clearance command value is corrected in the limited number of machining directions based on the data of the machining dimension errors corresponding to the limited number of machining directions as shown in fig. 6, but there is a possibility that the actual machining direction differs from the machining direction in which the data of the machining dimension errors are obtained. In order to cope with the above-described situation, in the wire electric discharge machine 100 according to embodiment 3 of the present invention, the side clearance correction value is obtained in an arbitrary machining direction, and the side clearance command value is corrected.

Specifically, the operator inputs data of the machining dimension error depending on the machining direction, which is obtained from the past machining result, to the side gap commander 46 via the data input/output device 120, as shown in fig. 6. The side clearance commander 46 can calculate a side clearance correction value in an arbitrary machining direction by performing interpolation calculation based on the data of the machining dimension error depending on the machining direction.

As a method for calculating the side clearance correction value in any machining direction by executing the interpolation calculation by the side clearance commander 46, the following modification is conceivable. First, the side clearance commander 46 may calculate the side clearance correction value in any of the machining directions by performing interpolation calculation based on the given data of the machining dimension error depending on the finite number of machining directions to obtain the data of the machining dimension error in any of the machining directions, and calculating the side clearance correction value in any of the machining directions based on the data of the machining dimension error. The side clearance commander 46 may calculate the side clearance correction value in a limited number of machining directions based on the data of the machining dimension error depending on the limited number of machining directions, perform interpolation calculation on the side clearance correction value in the limited number of machining directions, and calculate the side clearance correction value in any machining direction. The interpolation calculation method may be a method of performing linear interpolation or curvilinear interpolation between data, and is not limited as long as the method obtains the side gap correction value for the continuous machining direction.

According to the wire electric discharge machine 100 according to embodiment 3, the effect is achieved that fluctuations in the machining dimension error depending on the machining direction can be suppressed also in any machining direction other than the machining direction in which the data of the machining dimension error is obtained.

Embodiment 4.

In embodiments 1 to 3, the machining control device 111 or 112 needs to store the machining dimension errors or the side clearance correction values corresponding to the finite number of machining directions in the memory 202 or the storage device 203, and therefore, in the wire electric discharge machine 100 according to embodiment 4 of the present invention, reduction of the required data amount is achieved by approximating the data of the machining dimension errors corresponding to the finite number of machining directions by a function using a plurality of parameters.

[ formula 1 ]

[ formula 2 ]

Here, x and y of equation (1) are obtained by using equation (2) described above.

The plurality of parameters used for approximation may be calculated by applying the least square method to the data of the machining dimension errors corresponding to the limited number of machining directions, or may be directly input through the data input/output device 120 at the discretion of the operator. The calculation for approximating the data of the machining dimension error corresponding to the finite number of machining directions by a function using a plurality of parameters using a method such as the least square method may be performed by the machining control device 111 or 112, or may be performed outside the wire electric discharge machine 100. Specifically, the side gap commander 46 that receives the machining dimension error data via the data input/output device 120 may determine a plurality of parameters by performing parameter fitting using a method such as the least square method, or the side gap commander 46 may receive a plurality of parameters determined by an external computer via the data input/output device 120.

The side clearance commander 46 obtains a side clearance correction value corresponding to the machining direction θ based on a machining dimension error with respect to the machining direction θ such as the above-described e (θ) obtained from the plurality of parameters and the approximate function determined, and corrects the side clearance command value. The side clearance correction value may be calculated such that the machining dimension error becomes a constant value regardless of the machining direction based on the approximate value of the machining dimension error obtained from the plurality of parameters and the approximate function, and therefore, a value obtained by inverting the index of e (θ) may be used so that the machining dimension error becomes 0.

According to the wire electric discharge machine 100 according to embodiment 4, in addition to the same effects as those of embodiment 3, the number of the plurality of parameters used for approximation may be set to be smaller than the number of the data of the machining dimension error corresponding to the machining direction, and an effect of saving a storage area for storing in the memory 202 or the storage device 203 can be obtained.

The configuration shown in the above embodiment is an example of the contents of the present invention, and may be combined with other known techniques, and a part of the configuration may be omitted or modified without departing from the scope of the present invention.

Description of the reference numerals

1 an upper godet, 2 a lower godet, 3 a bobbin, 4 a supply roller, 5 a lower roller, 6 a recovery roller, 7 an X-axis drive device, 8 a Y-axis drive device, 9 a table, 13 a workpiece, 20 a drive control device, 30 a wire electrode, 31 an upper power supply, 32 a lower power supply, 33 an upper pusher, 34 a lower pusher, 35 a machining power supply, 40 an inter-electrode average machining voltage detection unit, 41 an inter-electrode average machining voltage correction unit, 42 a voltage calculation unit, 43 a machining speed control unit, 44 a target voltage storage unit, 45 a side gap estimator, 46 a side gap commander, 47 a side gap controller, 48 a target voltage correction unit, 49 a subtractor, 50 points, 51 distances, 100 a wire discharge machine, 111, 112 a machining control device, 120 a data input/output device, 201 CPU, 202 memory, 203 storage means, 204 display means, 205 input means.

Claims

1. A wire electric discharge machine which generates electric discharge between a workpiece and a wire electrode to machine the workpiece,

the wire electric discharge machine is characterized by comprising:

a drive control device that controls a relative distance between the wire electrode and the workpiece;

an average machining voltage detector for detecting an average machining voltage between the wire electrode and the workpiece;

a machining speed control unit that controls a machining speed via the drive control device based on the inter-electrode average machining voltage and a preset target voltage; and

a voltage correction unit that corrects either the average machining voltage between the electrodes or the target voltage so that a side gap between the wire electrode and the workpiece is constant regardless of a machining direction, based on machining information during machining and the machining direction,

the voltage correction unit includes:

a side clearance estimator that calculates an estimated value of the side clearance based on the machining information;

a side clearance commander that obtains a side clearance command value corresponding to the machining direction; and

a side gap controller that obtains a correction value so that the estimated value follows the side gap command value,

the machining speed control unit controls the drive control device so that the machining speed is set to a machining speed at which an absolute value of a voltage difference between the machining-gap average machining voltage corrected by the correction value and a preset target voltage is decreased, or controls the drive control device so that the machining speed is set to a machining speed at which an absolute value of a voltage difference between the machining-gap average machining voltage corrected by the correction value and the target voltage is decreased.

2. The wire electric discharge machine according to claim 1,

the side clearance commander obtains the side clearance command value corresponding to the machining direction by correcting the side clearance command value before correction with a side clearance correction value based on data of a machining dimension error depending on the machining direction.

3. The wire electric discharge machine according to claim 2,

the side clearance commander performs interpolation calculation on the data of the machining dimension error to obtain the side clearance correction value.

4. The wire electric discharge machine according to claim 2,

the side clearance commander approximates the data of the machining dimension error by a function using a plurality of parameters, and obtains the side clearance correction value based on the approximate value of the machining dimension error obtained from the plurality of parameters and the function.

5. The wire electric discharge machine according to any one of claims 1 to 4,

the machining information is the inter-electrode average machining voltage and the machining speed.

6. A wire electric discharge machining method for a wire electric discharge machine having a drive control device for controlling a relative distance between a wire electrode and a workpiece, the wire electric discharge machine machining the workpiece by generating electric discharge between the workpiece and the wire electrode,

the wire electric discharge machining method is characterized by comprising the following steps:

detecting an average machining voltage between the wire electrode and the workpiece;

controlling a machining speed via the drive control device based on the average machining voltage between the machining gaps and a preset target voltage; and

a step of correcting either the average machining voltage between the electrodes or the target voltage so that a side gap between the wire electrode and the workpiece is constant regardless of a machining direction, based on machining information during machining and the machining direction,

the step of performing the correction includes:

calculating an estimated value of the side clearance based on the machining information;

a step of calculating a side clearance command value corresponding to the machining direction; and

a step of obtaining a correction value so that the estimated value follows the side gap command value,

and a step of controlling the machining speed such that the absolute value of the voltage difference between the machining-gap average machining voltage corrected by the correction value and a preset target voltage is reduced, or controlling the drive control device such that the absolute value of the voltage difference between the machining-gap average machining voltage corrected by the correction value and the target voltage is reduced.