JPH0355123A - Electric discharge device - Google Patents

Abstract

PURPOSE:To reduce the consumption of a working electrode and to improve the accuracy in working by providing a detection circuit detecting the suspension of an electric discharging during the electric discharging duration. CONSTITUTION:On a down counter 12 the number of the pulses set on a set circuit 11 is set, the number of pulses impressed from an AND gate circuit 10 is subtracted and an arc cut time is measured. When a count up signal is impressed from a ring counter 9, the counting content so far is reset and the pulse number of the setting circuit 11 is set again. If the content of the down counter 12 becomes zero prior to the count up signal of the ring counter 9 being impressed, in other words, when the arc cut time within the time measured by the ring counter 9 becomes longer than the time set on the setting circuit 11, the count down signal is transmitted toward a monostable multivibrator 13 from the down counter 12, a light emitting diode 15 is lit to display the abnormality of the working state.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electric discharge machining device, and is particularly designed to prevent wear of a machining electrode and uneven surface roughness of a machined surface. This invention relates to electrical discharge machining equipment.

[Conventional technology]

In electric discharge machining, machining is performed by applying an intermittent machining current to a machining gap between a machining electrode and a workpiece.

In the areas of finishing machining and micromachining in such electric discharge machining, the machining current energy applied to the machining gap is set to be relatively small.

Therefore, even if a machining current is applied to the machining gap and discharge is started, the discharge state becomes unstable, and a so-called arc breakage phenomenon occurs in which the discharge is interrupted while the machining current is being applied.

When such an arc breakage phenomenon occurs, consumption of the machining electrode increases and the machining accuracy of the workpiece decreases. Furthermore, since the arc breakage phenomenon occurs irregularly, the machined surface roughness of the workpiece becomes non-uniform.

[Problem to be solved by the invention]

Therefore, when performing finishing or micromachining, while checking the machined surface roughness of the workpiece and the wear status of the machining electrode, change the machining conditions until the required machining accuracy is obtained. I was doing it.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an electric discharge machining apparatus that detects arc breakage during machining and oscillates an abnormal signal when arc breakage exceeds an allowable range.

Means for Solving the Problem] In order to achieve the above object, the present invention detects the arc breakage time that occurs within a certain period, and when the arc breakage time exceeds a preset time. , a detection circuit that oscillates an abnormal signal is provided.

[For production]

Then, when the arc cut-off time during processing exceeds a preset time, an abnormality signal is oscillated to indicate an abnormal state.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 and 2.

In the figure, 1 is a processing electrode. Reference numeral 2 denotes a workpiece, which is arranged to face the processing electrode 1 with a predetermined processing gap. Reference numeral 3 denotes a processing power supply device, which connects the processing electrode 1 and the workpiece 2. 4 is a DC power supply that outputs a preset voltage. 5 is a comparator, which is a processing power supply device 3
and is connected to DC power supply 4. Ru. Reference numeral 6 denotes a current detection circuit, which is connected to the processing power supply device 3. A pulse oscillator gate circuit 7 is connected to the current detection circuit 6 and the pulse oscillation circuit 7. A ring counter 9 is connected to the AND gate circuit 8. 10 is an AND gate circuit,
It is connected to the comparator 5 and the AND gate circuit 8. Reference numeral 11 denotes a setting circuit which sets the allowable arc breakage time within a fixed period of time using the number of pulses. 12 is a down counter, which is connected to the ring counter 9, the AND gate circuit 10, and the setting circuit 1l. 13 is a monostable multivibrator, which is connected to the down counter 12. 1
4 is a current limiting resistor, which is connected to the monostable multivibrator 13. 15 is a light emitting diode, which is connected to the current limiting resistor 14.

With such a configuration, the machining electrode 1 and the workpiece 2 are opposed to each other with a predetermined machining gap, and the machining power supply 3 is connected to the machining electrode 1 as shown in FIG.
Apply voltage and current having the waveforms shown in a) and (b). Then, an arc discharge is generated in the machining gap between the machining electrode 1 and the workpiece 2, and the workpiece is machined.

The pressure and machining current are A and A shown in Fig. 2 (a) and (b).
The waveform will look like B. However, if arc breakage occurs, the waveform will be as shown in c-F.

When a machining voltage is applied to the machining electrode 1, the comparator 5 compares the machining voltage with the voltage Ec applied from the DC power source 4 and outputs a waveform shown in FIG. 2(C).

The current detection circuit 6 outputs a waveform shown in FIG. 2(d) based on the current applied to the processing electrode 1. This waveform is the same as the current waveform applied from the processing electrode 3 regardless of arc breakage. On the other hand, pulse oscillator 7
From there, a reference clock pulse as shown in FIG. 2(e) is oscillated.

Therefore, from the AND gate circuit 8, as shown in FIG.
A pulse waveform as shown in is output, and the ring counter 9
When % is applied to the AND gate circuit 10, the ring counter 9 counts the number of pulses applied from the AND gate circuit 8, and calculates the time period during which the current is applied from the machining power supply device 3 to the machining electrode 1. measure. When the pulse count reaches a preset value, it oscillates a count-up signal to the down counter 12 as shown in FIG. Then start counting again from 1.

On the other hand, the AND gate circuit 10 outputs a pulse waveform as shown in FIG. 2(g) from the voltage waveform applied from the comparator 5 and the pulse waveform applied from the AND gate circuit 8.

The number of pulses set in the setting circuit 1l is set in the down counter 12, and the number of pulses applied from the AND gate circuit 10 is subtracted to measure the arc breakage time. Then, when a count-up signal is applied from the ring counter 9, the contents of the count up to that point are reset, and the number of pulses of the setting circuit 11 is set again.

If the content of the down counter 12 becomes O before the count up signal of the ring counter 9 is applied, that is, the arc expiration time measured by the ring counter 9 is set in the setting circuit t1. When it becomes longer than the time, a count 1 down signal as shown in FIG. 2(i) is oscillated from the down counter 12 toward the monostable multivibrator l3.

The monostable multivibrator 13 to which the countdown signal has been applied oscillates an activation signal for the light emitting diode 15 as shown in FIG. let

In this way, by detecting and displaying abnormalities in the machining state during electrical discharge machining, it is possible to change the machining conditions during machining, reducing wear on the machining electrode and improving machining accuracy. I can do it.

Moreover, the surface roughness of the processed surface can be improved.

Furthermore, since machining conditions can be changed during electrical discharge machining, workability can be improved.

In the above embodiment, the detection time of arc breakage is the time during which the machining current is applied to the machining electrode 1, but it may be a constant time regardless of the presence or absence of the machining current. Moreover, although the light emitting diode 15 is used to indicate an abnormality, this display method may also use display means such as light or sound.

Furthermore, it may be displayed on the display screen of the control device of the electrical discharge machine.

Further, in the above embodiment, when an abnormality is detected, the abnormality is simply displayed, but the electric discharge machining may be stopped upon activation of the light emitting diode 15 {tJV.

〔Effect of the invention〕

As described above, according to the present invention, since a detection circuit for detecting arc breakage that is harmful to electric discharge machining is provided, wear of the machining electrode can be reduced and machining accuracy can be improved.

Furthermore, the roughness of the machined surface of the workpiece can be improved.

[Brief explanation of drawings]

FIG. 1 is a current and voltage waveform diagram illustrating the operation of an example of the detection circuit of the present invention. l: Machining electrode, 2: Workpiece, 3: Machining power supply, 4: DC power supply, 5: Comparator, 6: Current detection circuit, 7: Pulse oscillator, 8: AND gate circuit, 9: Ring counter, 10
NAND gate circuit 11: setting circuit, 12: down counter, 13: monostable multivibrator 14: resistor, l5: light emitting diode.

Claims (1)

[Claims] 1. In an electrical discharge machining device that performs machining by applying a pulse voltage to the machining gap between the machining electrode and the workpiece to generate intermittent arc discharge, a detection circuit that detects interruptions in discharge during the discharge duration. An electrical discharge machining device characterized by being provided with.