JPH09248717A - Controller of wire electric discharging machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aim at improvement in working accuracy by restricting the vibration of a wire electrode as well as surely detecting the vibratory behavior of the wire electrode in a wire electric discharging machining device. SOLUTION: Voltage detecting means (101, 102, 103) for detecting voltages in a machining gap and a band pass filter 110 for allowing passage through a preset frequency band range based upon the proper vibration relating to the wire electrode between guides from the output signals of a voltage detecting means are provided. Also a comparator 111 for comparing the output of the band pass filter 110 with a preset reference voltage is provided so as to control the supply of machining pulses so that the supply of machining electric current may be stopped on the basis of the output of the comparator. In addition, a differentiator for differentiating the output of the band pulse filter 110 is provided so as so control the supply of the machining pulse so that the supply of machining electric current may be stopped on the basis of the output of the differentiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly accurate wire electric discharge machine, and more particularly to a controller for a wire electric discharge machine which suppresses vibration of a wire electrode to improve machining accuracy.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional wire electric discharge machine. In the figure, 1 is a wire electrode, 2 is a workpiece, 3 is a set of wire guides for guiding the wire electrode 1 at the upper and lower portions, 4 is a table on which the workpiece 2 is placed, 5a and 5b are electrodes 1 The X-axis and Y-axis drive motors for positioning the relative position between the workpiece 2 and the workpiece 2, 6 is an axis drive control device for controlling the X-axis and Y-axis drive motors 5a, 5b,
7 is a machining power supply that supplies a discharge current pulse to the machining gap 3 between the wire electrode 1 and the workpiece 2, 8 is a machining power supply control circuit that controls the switching operation of the machining power supply 7, and 9 is machining between the gaps. A voltage detection circuit 10 for detecting a voltage, an NC device 10 for sending an axis movement command and a machining condition parameter to the axis drive control device 6 and the machining power supply control circuit 8.
Is an NC program. FIG. 7 is a diagram showing an example of a machining power supply device, 701 is a DC power supply for supplying machining current between the electrodes, 702 is a switching element which is controlled to be turned on and off by a machining power supply control circuit, and 703 is a pole. A limiting resistor 704 that limits the value of the current flowing between them and a capacitor 704 are connected in parallel between the poles.

Next, the operation will be described. NC device 10
The machining path information and machining electrical condition parameters are input to the NC program 11 or the operation panel (not shown). The input processing electric condition parameter is output to the processing power supply control circuit 8. Processing power control circuit 8
Generates a drive signal having a predetermined current peak, pulse width, and rest time based on this parameter, and controls the machining power supply 7. The machining power source 7 is driven by this drive signal, and a predetermined current pulse is supplied to the machining gap between the wire electrode 1 held by the wire guide 3 and the workpiece 2 above and below the workpiece 2. Generally, electric discharge machining is performed by supplying water or a water-based machining liquid to the machining gap. FIG. 8 is a diagram showing a waveform between electrodes,
8A shows the machining voltage, and FIG. 8B shows the machining current. The machining gap voltage is the DC power supply 701 as shown in FIG. 8A until the discharge is started after the switch element 702 in FIG. 7 is turned on. Voltage E1 and the machining gap voltage decreases to the arc potential with the start of discharge, and as shown in (b), the switch element 702 remains on for a predetermined time TON, and the DC power source 701 is applied to the machining gap. Of the voltage E1, the limiting resistor 703, the constant of the capacitor 704, etc. are supplied. After that, switch element 702
Turns off, and the off time continues for a predetermined time TOFF,
The above operation of turning on the switch element 702 is repeated. At the same time that the electric discharge is generated between the wire electrode and the workpiece as described above, a positioning command is output to the drive control device 6 based on the machining path information, and the X-axis drive motor 5a and the Y-axis drive motor 5b move the table 4. A desired shape is processed by performing the positioning control.

[0004]

The conventional electric discharge machining apparatus is constructed as described above and uses a wire having no rigidity for the machining electrode, which causes a vibration of the wire electrode during machining. It causes drum shape and shape error at the corners of the processed shape. To solve this problem, Japanese Patent Application Laid-Open No. 54-109698 discloses a technique of setting a dwell time according to the frequency of a wire electrode to improve the precision of machining by eliminating machining chips. There is no description of the technology to suppress the. Also, JP-A-53-2
Although a technique for suppressing wire vibration by applying high-frequency vibration to 4699, 54-90691, 55-137840 and the like has been disclosed, the purpose is to change the vibration mode or to eliminate the machining waste. Also, Japanese Patent Application Laid-Open No.
Although 20495 discloses a technique for actually measuring wire electrode vibration, a complicated detection device is required.

The present invention has been made to solve the above problems, and is inexpensive in a wire electric discharge machine.
Moreover, it is an object of the present invention to realize a vibration detecting device that accurately detects the vibration behavior of the wire electrode, and further to suppress the vibration of the wire electrode from the vibration behavior of the wire electrode to improve the machining accuracy.

[0006]

According to a first aspect of the present invention, there is provided a control device for a wire electric discharge machine, wherein a wire-shaped electrode which travels under tension between a plurality of guides for guiding and supporting the travel of the wire-shaped electrode and a desired shape. In a controller of a wire electric discharge machine for detecting a state of a machining gap formed by a workpiece to be machined and controlling a machining pulse supplied to the machining gap, a voltage detection for detecting a voltage of the machining gap. Means and
A band pass filter (band filter) that passes a predetermined frequency band based on the natural vibration of the wire electrode between the plurality of guides from the output signal of the voltage detection means is provided.

A controller of the wire electric discharge machine according to a second aspect of the present invention is the same as the controller of the wire electric discharge machine of the first aspect, further comprising a comparator for comparing the output of the bandpass filter with a predetermined reference voltage. The machining pulse is controlled so as to stop the supply of the machining current based on the output of the comparator.

A control device for a wire electric discharge machine according to a third aspect of the present invention is the same as the control device for a wire electric discharge machine according to the first aspect, further comprising a differentiator for differentiating the output of the bandpass filter. Based on this, the machining pulse is controlled so as to stop the supply of the machining current.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. Embodiment 1 of the present invention will be described with reference to the drawings. 1 is a connection diagram showing a wire electric discharge machine for explaining a first embodiment of the present invention. The overall configuration of the wire electric discharge machine and the machining power supply device are the same as those of the conventional example shown in FIGS. 7 and 8, respectively, and therefore description thereof is omitted.

FIG. 1 is a diagram showing details of a control circuit according to a first embodiment of the present invention. In the figure, 101 is a contact, 10
Voltage dividing resistors 2 and 103 detect the potential of the wire electrode by converting it into a predetermined voltage value according to the ratio of the resistance values of the voltage dividing resistors 102 and 103. Reference numeral 104 denotes a low-pass filter, which includes a variable resistor 105 and a capacitor 106. The input end of the low-pass filter 104 has a voltage dividing resistor 10
2 and 103. Reference numeral 107 denotes a high-pass filter, which includes a capacitor 108 and a variable resistor 109, and the input end of the high-pass filter 107 is connected to the output end of the low-pass filter 104. The low-pass filter 104 and the high-pass filter 107 constitute the band-pass filter 110, and the variable resistor 1
05 and 109 are set to predetermined values to set the pass band. Further, 111 is a comparator, and 112 is FIG.
A pulse oscillator for controlling the switching of the switching element 702 shown in FIG. 1, 113 is an inverter circuit, one of the input terminals of the comparator is connected to the output terminal of the bandpass filter 110, the other is held at a predetermined potential, and the output terminal Is connected to the input terminal of the inverter circuit 113. Reference numeral 114 is a NAND circuit, 115 is an AND circuit, and one input end of the NAND circuit has an inverter circuit 11
The third output is connected to the output end 112a of the pulse oscillator, and only the signal of the machining current ON time TON is output to the output end 112a. The output terminal of the NAND circuit 114 is connected to one input terminal of the AND circuit 115,
One input end of the AND circuit 115 is connected to the output end 112b of the pulse oscillator, the switching control signal of the switching element 702 is output to the output end 112b, and the output end of the AND circuit 115 is connected to the switching element. There is.

Next, the operation of the control circuit according to the first embodiment will be described with reference to the drawings. FIG. 2 is a diagram showing an example of the output signal of each part of FIG. 1, 201 is the input signal waveform of the bandpass filter 110, that is, the voltage between contacts,
Reference numeral 202 denotes an output waveform of the bandpass filter 110, 20
3 is the output waveform of the comparator 111, 204 is TON, that is, the output waveform of the pulse oscillator 112a, 205 is the oscillation stop signal, 206 is the output waveform of the pulse oscillator 112b, 2
Reference numeral 07 is an output waveform of the AND circuit 115.

The meaning of the output signal 202 of the bandpass filter 110 will be described with reference to FIG. The figure shows the behavior of vibration of the wire electrode when the wire electrode 1 processes a workpiece, and is an example of rough machining, that is, machining a groove. The vibration of the wire electrode is generally caused by the primary, secondary, and
It is formed by superposition of higher-order vibration modes such as the third order .... When the wire electrode further vibrates, the discharge starts when the distance between the wire electrode and the workpiece is reduced to a certain extent, and ends when it is separated to a certain extent. I know I will. Therefore, the closer the wire electrode 1 is to the workpiece 2, the higher the discharge frequency and the no-load time T
The inter-electrode voltage decreases as d becomes shorter, and conversely, if the wire electrode 1 moves away from the workpiece 2 and the discharge frequency decreases, the no-load time Td increases and the inter-electrode voltage increases. . In particular, if the workpiece 2 is in the center of the wire guide 3, the distance between the wire electrode and the workpiece is considered to be most affected by the first-order vibration mode. The frequency of the primary vibration mode is a value close to the natural frequency that can be obtained from the linear density m determined by the distance z between the wire guides, the wire tension T, the material of the wire electrode and the wire diameter, and the secondary is the value. Times, and the nth order becomes n times. The first-order natural frequency p is given by Equation 1.

[Equation 1] Therefore, the variable resistor 105 and the variable resistor 109 are configured so as to form a bandpass filter that passes the frequency range near the first-order natural frequency obtained by the above equation and up to the second-order natural frequency at the maximum. By setting the parameter (1) and removing the second natural frequency band or higher, a signal close to the wire vibration waveform can be output. Similarly, the wire guide 3
The optimum mode for detecting the vibration of the wire electrode 1 may be selected according to the positional relationship between the workpiece 2 and the workpiece 2, and the frequency bands other than the other modes may be removed.

Next, the comparator output 203 outputs "1" when the output signal 202 of the bandpass filter 110 is higher than the reference potential Vc. That is, by determining the predetermined Vc corresponding to the relative distance between the wire electrode 1 and the workpiece, it is possible to detect that the wire electrode 1 has approached the workpiece 2 by a predetermined distance. When a predetermined pulse ON time TON is output from the pulse oscillator 112 as in 112a to 204, an oscillation stop signal such as 205 is output to the output of the NAND circuit 114. From this signal and the output waveform of the pulse oscillator 112b indicated by 206, the
The D signal is output as 207. That is, when the wire electrode is closer to the workpiece than the predetermined distance, TON
Since the switching element 702 for the time is stopped, the external force due to the discharge does not act, the vibration amplitude of the wire electrode does not increase, and the vibration of the wire electrode is efficiently suppressed.

Embodiment 2 FIG. A second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a connection diagram showing details of the control circuit according to the second embodiment of the present invention. In the figure, the contactor 101, the voltage dividing resistors 102 and 103, the bandpass filter 110, and the pulse oscillator 112 are the same as those shown in FIG. 401 is a differentiating circuit, a capacitor of 402, a resistor of 403,
405 is a comparator, 406 is an inverter circuit, one of the input terminals of the comparator is connected to the output terminal of the differentiating circuit 401, the other is held at a predetermined potential Vc, and further the output terminal Is connected to the input terminal of the inverter circuit 406. 40
7 is a NAND circuit, 408 is an AND circuit, and NAN
One input end of the D circuit 407 is connected to the output of the inverter circuit 406 and the other end is connected to the output end 112a of the pulse oscillator. The output end 112a has a machining current ON time TO.
Only N signals are output. The output end of the NAND circuit 407 is connected to one input end of the AND circuit 408, and
One input end of the D circuit 408 is the output end 1 of the pulse oscillator.
12b, and the switching control signal of the switching element 702 is output to the output end 112b.
The output terminal of the ND circuit 408 is connected to the switching element.

Next, the operation of this control circuit will be described with reference to the drawings. FIG. 5 is a diagram showing an example of the output signal of each part of FIG. 4, 501 is the input signal waveform of the bandpass filter 110, that is, the voltage between contacts, 502 is the output waveform of the bandpass filter 110, and 503 is the derivative. Circuit 4
01 is an output waveform, 504 is an output waveform of the comparator 405, 505 is TON, that is, an output waveform of the pulse oscillator 112a, 506 is an oscillation stop signal, and 507 is the pulse oscillator 1.
12b is an output waveform, and 508 is an output waveform of the AND circuit 408. Output signal 50 of bandpass filter 105
2 and the output signal 505 of the pulse oscillator 112b are the same as those in the first embodiment shown in FIG.

In the differentiating circuit 401 in FIG. 5, a + potential is output when the value of the output signal of the high-pass filter 107 decreases, and conversely, a-potential is output when the value of the output signal 502 increases. Furthermore, by setting the comparison voltage of the comparator 405 to a predetermined negative potential between the negative potential output from the differentiating circuit 401 and 0V,
When the value of the output signal of the high pass filter 105 increases, "0" is output, and otherwise "1" is output.
That is, the output signal of the comparator 405 is "1" when the wire electrode 1 approaches the workpiece 2 and is stopped, and conversely "0" when the wire electrode 1 separates from the workpiece 2. Is output. As a result, the first embodiment
Similarly, the control circuit of the present embodiment operates so as to stop switching of the TON time when the wire electrode 1 separates from the workpiece 2. Therefore, no electric discharge is generated when the wire electrode 1 separates from the workpiece 2, so that the discharge repulsive force acting on the wire electrode 1 acts only in the direction of suppressing the vibration of the wire electrode, thereby suppressing the vibration of the wire electrode. You can

[0017]

According to the first aspect of the present invention, by extracting a predetermined wire electrode vibration component from the processing voltage signal, it is possible to detect the approaching and separating behavior of the wire electrode with respect to the workpiece and its distance. .

According to a second aspect of the present invention, when the amplitude of the wire electrode exceeds a predetermined value, the supply of the discharge current is stopped, so that the increase of the vibration of the wire electrode can be suppressed, and the drum accuracy can be improved. It is possible to improve processing accuracy such as shape accuracy of corners.

In the third aspect of the invention, the discharge is stopped when the wire electrode is separated from the workpiece, so that the discharge repulsive force can act only in the direction of stopping the vibration of the wire electrode. Furthermore, the vibration of the wire electrode can be suppressed more efficiently, and the processing accuracy such as drum accuracy and corner shape accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a connection diagram showing a control circuit according to a first embodiment.

FIG. 2 is a timing chart showing the operation of the control circuit according to the first embodiment.

FIG. 3 is a diagram illustrating a vibration mode of the wire electrode according to the first embodiment.

FIG. 4 is a connection diagram showing a control circuit according to a second embodiment.

FIG. 5 is a timing chart showing the operation of the control circuit according to the second embodiment.

FIG. 6 is a block diagram showing a wire electric discharge machine for explaining a conventional example.

FIG. 7 is a connection diagram showing an example of a conventional processing power supply device.

FIG. 8 is a diagram showing a waveform between electrodes of a conventional wire electric discharge machine.

[Explanation of Codes] 1 ... Wire electrode, 2 ... Workpiece, 3 ... Wire guide, 7 ... Machining power supply, 8 ... Machining power supply control circuit, 101 ... Contact Child, 102 ... Dividing resistance,
103 ... Voltage dividing resistor, 110 ... Band pass filter, 111 ... Comparator 401 ... Differentiation circuit, 405 ... Comparator

Claims (3)

[Claims] 1. A state of a machining gap formed by a wire-shaped electrode traveling under tension between a plurality of guides for guiding and supporting the traveling of the wire-shaped electrode and a workpiece machined into a desired shape is detected. In the controller of the wire electric discharge machine for controlling the machining pulse supplied to the machining gap, the voltage detection means for detecting the voltage of the machining gap, and the output signal of the voltage detection means between the plurality of guides are used. A control device for a wire electric discharge machine, comprising a bandpass filter (bandpass filter) that passes a predetermined frequency band based on the natural vibration of the wire electrode. 2. The control device for a wire electric discharge machine according to claim 1, further comprising a comparator for comparing the output of the bandpass filter with a predetermined reference voltage, and supplying the machining current based on the output of the comparator. A control device for a wire electric discharge machine, characterized in that a machining pulse is controlled so as to stop. 3. The control device for a wire electric discharge machine according to claim 1, further comprising a differentiator for differentiating the output of the bandpass filter, and machining so as to stop the supply of the machining current based on the output of the differentiator. A control device for a wire electric discharge machine characterized by controlling pulses.