JPS6161711A - Power source for electric discharge machining - Google Patents

Abstract

PURPOSE:To expedite the recovery of short-condition between electrodes to aim at stabilizing arc-discharge machining, by detecting the short condition between the electrodes to adjust the turn-on and -off time of a switching element. CONSTITUTION:When the short condition between electrode is established, a short detecting circuit 25 determines the level of the detected short condition, and delivers a signal to an oscillator OSC2 which issue therefore, an turn-on and -off signal. That is, when the short condition is established, at first the turn-on condition is established and then the turn-off condition is established. With the repetition of this turn-on and turn-off conditions, when the short condition is released, the oscillation is ceased. Therefore, the turn-on and -off time widths of an oscillators 22 is changed in accordance with an area to be machined, and therefore, when the time width of thinned-out operation is decreased, the machining may be stabilized even if an area to be machined is large.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an electric discharge machining power supply, and in particular to an electric discharge machining power supply that can easily recover from a short circuit between electrodes and can perform stable electric discharge machining. FIG. 3 is a block diagram of electrical discharge machining, in particular, a wire-cut electrical discharge machine. In the figure, 1 is a power source for electrical discharge machining, 2 is an upper wire guide, and 3 is a lower wire guide.

4 is an XY table, 5 is a workpiece, 6 is a wire electrode, 7 is an X-axis servo motor, 8 is a Y-axis servo motor, 9 is a machining liquid treatment tank, and 10 is a CNC 111 is a machining instruction tape.

A pulsed voltage is generated from an electric discharge machining power supply l that generates an electric discharge between the workpiece 5 and the wire electrode 6, and is applied between the wire electrode 6 and the workpiece 5. The specific configuration of this electric discharge machining power source will be explained in detail.

FIG. 4 shows a transistor-controlled capacitor discharging circuit in which a switching element using a transistor is inserted into the charging circuit portion of the discharging circuit for capacitor C.

According to this figure, the peak Ip of the discharge current can be changed by switching the transistors Tri and Tr2 using the control circuit. In this circuit, the power supply and the poles can be isolated by a switch circuit, so when a discharge current is flowing, the power supply can be cut off, and current can be prevented from flowing in a state where insulation recovery is not achieved. In addition, as shown in Fig. 5, wire electrical discharge machines, small hole drilling machines, and cemented carbide materials are advantageous for machining with a current having a high peak value Ip and a narrow pulse width τp, which is difficult to obtain with a transistor power supply. Widely used as a power source for specialized processing machines.

(Problems with the conventional technology) However, in response to the demands of the times for automation and labor saving in electric discharge machining, the joting status of electric discharge machining cannot be fully automatically monitored and discharged without human intervention. Increasingly, there is a need for a device that can perform one-step processing. For example, if a short circuit between electrodes persists during electrical discharge machining, if the machining conditions can be changed accordingly, automation and labor savings can be promoted, and workpieces will not be wasted. ,Also,
This will contribute to improving the reliability of processed products.

Under these circumstances, such technical improvements are strongly desired in this technical field.

(Objective of the Invention) It is an object of the present invention to provide an electric discharge machining power source that automates work and saves labor, and also allows easy recovery of show between machining areas and stable discharge JY application.

(Summary of the Invention) The present invention provides a means for detecting a short-circuit condition between electrodes in an electric discharge machining power source that performs electric discharge machining by charging and discharging a capacitor by turning on and off switching elements, and a means for detecting a short-circuit condition between electrodes, and Means for obtaining a signal regarding the machining area based on the current signal and the servo feed rate, and means for adjusting the off time of the switching element in accordance with the signal regarding the machining area are provided.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Fig. 1 is an overall configuration diagram of the electrical discharge machining power source according to the present invention;
The figure is a waveform diagram of each part in FIG. 1. In the figure, 21 is a normal on/off oscillator, whose waveform diagram is shown in FIG. 2(a).

Reference numeral 22 denotes an oscillator used to thin out the on signal of the oscillator 21, and the off time can be changed by changing the time constant formed by an external resistor and capacitor. 23 is an AND circuit, 24 is an amplifier, Tr is a switching transistor, R1 is a charging resistor, R2 and R3 are voltage dividing resistors for detecting the voltage between electrodes,
R4 + size machining current detection resistor, C is a capacitor, 25 is a short circuit detection circuit, 26 is a differential amplifier that outputs a speed proportional signal, 27 is a smoothing circuit that smoothes the speed proportional signal, 2
8 is a divider, 29 to 31 are ratio 1 calculators, 32 to 34 are relay coils, 3 is a relay contact, R is a resistance, Co, CL to C3 are capacitors, 35 is a voltage /
It is a frequency converter.

Next, the operation of the electrical discharge machining power supply will be explained.

Normally, the switching transistor Tr that turns on/off the discharge circuit of the capacitor C is turned on/off even with the waveform of 05CI shown in FIG. 2(a). Furthermore, 03
C2 is the 21st Cd) (As shown, since the signal 110 is input to the ONIHA signal or the A N D Liffii path 23, the signal that depends only on the output signal of the 03CI is the A
The output signal is output from the ND circuit 23, and the output signal is sent to the amplifier 24.
The signal is amplified and turns on/off the switching transistor Tr. On the other hand, the voltage Eg between the electrodes is configured to be monitored via voltage dividing resistors R2 and R3 connected between the electrodes.

Therefore, in the present invention, when a short circuit occurs between poles, 03C2 is turned on/off to thin out the on signal from 03CI.

This point will be explained.

When the gap between the electrodes becomes short-circuited and, for example, the voltage Eg between the electrodes takes a waveform as shown in FIG.
A short detection signal SS is output as shown in C). When the short detection signal SS is input to the oscillator 03C2, the oscillator 05C2 outputs an on/off signal as shown in FIG. 2(d). In other words, when you short circuit, it starts from on and then turns on and off repeatedly.

When the short circuit is released, oscillation is stopped and set to 1-. Therefore.

The on/off signal of the output signal from 05CI is this ○SC
It will be logically ANDed with the on/off signal of 2. In other words, the ON signal of 03CI is thinned out by the ON/OFF signal from ○S02.

By the way, in the present invention, the off-time width is further configured to be changed depending on the processing area. 3, the machining area Sm is proportional to the value obtained by dividing the machining current Im by the machining speed j\Fm. That is, Sm=Ks (Im/Fm) where K is a constant.

Therefore, the machining current In is obtained via the machining current detection resistor R4, and the machining current signal X is input to the divider 28.

On the other hand, since the machining speed Fm is proportional to the difference between the average machining voltage and the servo reference voltage, the signal from the servo system and the machining voltage E
The signal from g is input to a differential amplifier 26), and the differential amplifier 26 outputs a machining speed proportional signal Y6).
The signal is passed through a smoothing circuit 27 to a Hashimoto divider 28 where it is smoothed. Therefore, the 1 divider 28 divides the machining current signal X by the machining speed proportional signal Y, and outputs the machining area proportional signal Z. The level of this signal Z is compared by comparators 01 to C5 to which reference voltages VLI to VL3, which are set in stages, are connected, respectively, and relay coil RL is selected according to the level of processing area proportional signal Z at 7. ~RL
Energize 3. In other words, when the output of machining area proportional signal 2 is high, relay coil RLl to RI, 3 is energized, contacts rl to r15 are opened, and the off time of the I word output from 0SC2 is short. It becomes like this.

In this way, the on/off time width of 0SC2 can be changed depending on the processing area. If the short-circuit condition continues, the normal switching transistor Tr
By thinning out the on/obverse state, it becomes easier to recover from the short-circuit condition. However, when processing materials with a small processing area, it is necessary to thin out the switching pulse and
1. If the width is made smaller, processing becomes very stable. Therefore, the electrical discharge machining power supply is short-circuited! ! - It is possible to recover stable electrical discharge machining efficiently.

Here, the circuit configuration for swifting the switching transistor Tr and the circuit configuration for thinning out pulses according to the processing area are configured to be executed in a numerical control (NC) device having a microphone cocomputer. It goes without saying that you can. especially,
The feed speed signal is obtained directly from the NC device,
In the NC device, the machining current signal obtained from the current detector is divided by the feed rate signal to obtain the machining area, and the signal is used to directly control the on/off of the switching transistor Tr by changing the pulse thinning range. It can also be configured to output from the NC device.

Further, in this example, the off time of 03C2 is set to three stages, but it goes without saying that it may be set to 17 so that it can be set more precisely, or it may be set coarser.

(: Effect of the invention) According to the present invention, is it possible to charge/discharge the capacitor by turning on/off the switching element? In an electric discharge machining power supply that performs electric discharge machining, means for detecting a short-circuit condition between machining electrodes, and means for obtaining a signal regarding the machining surface 1M based on a machining current signal and a servo feed rate in the short-circuit condition;
Since the apparatus is provided with means for adjusting the off-time of the switching element in accordance with the signal related to the machining area, it is possible to automate electric discharge machining and save labor without manual intervention. In addition, when there is a short-circuit between the machining areas, the off-time of the switching element can be adjusted taking into account the machining area, which speeds up the recovery from the short-circuit between the machining areas and stabilizes electrical discharge machining! ! 6.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of the electric discharge machining power supply according to the present invention, Fig. 2
The figure is a waveform diagram of each part in Figure 1, Figure 3 is an overall diagram of the system before discharge, Figure 4 is a diagram of a conventional capacitor discharge circuit with transistor control, Figure 5 is the voltage in Figure 4,
It is a waveform diagram of public opinion. 21.22... Oscillator, 23... AND circuit, 24
...Amplifier, 25...Show I circuit, 26...
Differential amplifier, 27... Smoothing circuit, 28... Divider, 29-31... Calibrator, 32-34... Relay coil. Patent applicant: Fananku Co., Ltd. Agent: Minoru Tsuji (1 other person)

Claims (1)

[Claims] In an electric discharge machining power source that performs electric discharge machining by charging and discharging a capacitor by turning on and off a switching element, there is provided a means for detecting a short-circuit condition between electrodes, and a means for detecting a short-circuit condition between machining electrodes based on a machining current signal and a servo feed rate. An electric discharge machining power supply comprising: means for obtaining a signal regarding the machining area; and means for adjusting an off time of a switching element in accordance with the signal regarding the machining area.