JPS5937018A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To prevent failure of working by performing frequency spectral analysis of the inter-pole gap discharge waveform and deciding between normal and abnormal discharge thus deciding whether the inter-pole gap state is normal or not. CONSTITUTION:Frequency spectrum of discharge voltage waveform in the gap between the electrode and workpiece is analyzed to identify between normal and abnormal discharge states by means of an abnormal discharge detecting means. For any state of spectrum, high output having frequency f0 corresponding to the reciprocal number of period (T) is produced. If the output is low for fo high for fH, it can be considered to be normal discharge. Consequently abnormal discharge can be identified.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus, in particular, an electric discharge machining apparatus, in which an electrode and a breaking material are placed facing each other with an insulating machining liquid interposed therebetween, and an electric discharge is generated in the gap between the electrodes. Electrical discharge machining equipment (related to this) that processes corrugated objects.

FIG. 1 shows a schematic diagram of a conventional discharge device. In FIG. 1, -C1 electrode + 01; r workpiece 14 and insulation addition 1''
They face each other with a liquid 16 in between. Electrode 10 and workpiece 14
A processing power supply 18 is connected between them.
It is composed of a compensating resistor I Rc, an oscillator I Rd for controlling the intermittent switching of the switching element 18)), and an oscillator I Rd for controlling the intermittent switching of the machining current between the electrode 10 and the object 14. A is supplied to the gap 20 between the poles.

The machining current I shown in "I=-ξ]" can be expressed by the following formula: I=-ξ]Ku (r is the voltage value of the DC electric bed source 1811, R is the resistance value of the current limiting resistor IFlc, and v9 is the voltage value between electrodes). Voltage value between electrodes v9 is 20 to 30V during arc discharge, OV during short circuit.
1 During unused power, it becomes F and V, and the switch nog element 181
) is in the A state (yoOV).

Therefore, by detecting this inter-electrode voltage value v9 and averaging it in the smoothing circuit 22, it is possible to control the inter-electrode gap using this value. That is, when the inter-electrode gap 20 is wide, discharge is difficult to occur and the average voltage value Vs is high. When the distance between the electrodes [20] is narrow, short circuits may occur or the average voltage value Vsl will easily drop. Therefore, if the average voltage value Vs of B is compared with the reference voltage value Vt, and the difference between B is amplified by the amplifier 24 and the hydraulic servo coil 26 is turned on, the hydraulic pressure generating pump 28 and the hydraulic pressure generator 30 are (41"C is applied to the hydraulic servo +1 mechanism, which is formed in 1), and the electric current (Qi + O) is controlled so that the gap 20 between the poles is approximately - constant.

When determining whether the machining condition is good or bad with conventional electric discharge machining equipment, the most common method is the average voltage value VC of the voltage between the machining points ■9 mentioned above.
, ie observed. The average voltage value Vs
When is low, the inter-electrode impedance is low, resulting in short circuits and continuous arc discharge, and processing powder and sludge may remain in the inter-electrome gap 20. However, the most dangerous abnormal arc discharge in electric discharge machining is that once it occurs, carbon is generated due to thermal decomposition of the machining fluid, resulting in an electric discharge between the carbon and the workpiece, resulting in a high machining innovator. become. Observation of the average voltage value Vs at t:Me in Part B-C is the detection of deterioration of the electrode gap condition due to abnormal arc discharge 1.1. There is a drawback that it is impossible:
.

The present invention has been made in view of the conventional problems mentioned in m1-C
The purpose of this is to analyze the frequency spectrum of the voltage waveform of the gap discharge during the occurrence of a negative electric current, to distinguish between normal and abnormal discharges, and to determine whether the condition of the gap between the electrodes is normal or not.
To provide an electrical discharge machining device that has the following features.

In order to achieve the object of item 11, the present invention (i.e. electrode and wave
1. The workpiece is placed facing the object with an insulating upper liquid interposed therebetween, and an electrical discharge is generated in the opposing gap. The frequency spectrum of the collected voltage waveform between the electrode and the workpiece is analyzed in the power applying device 1ζ, 1, 1. j Normal father type 1m and i "normal h (Identify whether it is in the electric state 1 - abnormal discharge detection 1 stage, and according to the above analysis 4 - c4' f4 bow output according to the gap state between the poles) Equipped with a means for determining the state between extremes: special effects and 4ro.

Hereinafter, a preferred embodiment of the present invention will be explained based on the drawings. Fig. 2 shows a hk lightning voltage waveform, without showing its frequency spectrum, for explaining the detection principle in the present invention. and lj'i as in the case of no discharge.

In the case where only a voltage pulse Li is applied without electric current υ (this can be expressed relatively easily mathematically) (by the way, the amplitude E2 period '1
The spectrum when the pulse width is r can be expressed as follows. (17 However, in the case of the force field waveform, it is an atlanatum, and the formula is @It t.) and t! , ω-27t= ■ In Figure 2, spectrum diagram 1. The case of t '1''=2r is described as an example.The spectral distribution of B and jllll
The following items can be found in the previous state.

(1) The spectrum of the state Izil is also the reciprocal of the period ゛1゛. In the case of normal discharge, the peak value is low compared to the others at 71:t7.

(Related to 217'-), high frequency [1,+ (approximately 2M, l+, or more) does not exist, and in the case of normal discharge, it is around 200M+-1□. This occurs because the high frequency components are not attenuated.

(The output at 3110 is (IE<, the output at IN is 11
If it lasts for 30 minutes, it will be considered normal discharge.

From the above results, it can be determined that the condition is in the ``cone shape 11μ'' of item (3), and it can be seen that the abnormal weave in the A1 state is ijJ function.

FIG. 3 shows this embodiment. ! The structure is basically the same as that of a frequency spectrum analyzer. By using the voltage signal F (tl is the output No. 8 fft of the FM modulation error 51) of the gap between the poles and the mixer, -(mixing i]・\wo log-in detection, F(t) and f(t) are obtained.
Only the frequency of the intermediate frequency j (tl) is taken out of the sum of the frequencies, and the first difference is also obtained. , the ↓ amplitude is detected by the detector 54 (low frequency amplifier 55 (amplified by ζ).The above-mentioned FM modulator 5
1 is analogous to the fact that the voltage Aν is changed in proportion to time (from this, time and frequency are The relationship becomes linear, and the amplitude of the frequency spectrum that is equal to the frequency of ``(t) of Fft) can be taken out as the output of the low frequency amplifier 55 for each time. The time when Aν reaches 1 voltage corresponding to the above f, I14 can be determined by accurate oscillation +M56 and a counter 57 that counts this output. 58 is a fo discriminator, and 59 is a small discriminator. The content of the counter 57 becomes the ablog voltage Aν of the D/'A converter 601, which modulates the FM modulator 51. In response to a timing signal, the frequency is amplified below a predetermined reference value at that timing.
~of! , is large or small (7. Based on this result, output SA is output in case of abnormal discharge. For example, f. or 3 K
H□ fH is 5 M 112 and some. 2↓l: If the intermediate frequency is 10.7M112 and A1, then f(t) is 10.
At the time of 693M +-12 [. is 5.700 M I+
2, each spectrum of "," is detected.FM modulator 5
1 is in a wide 4fF range, and when the human power is OVO! '
When i M Ilz is 10 V, it is 10 M I+, and if the 1)/Δ conversion is I 6 b i ambiguous, it becomes a subexample analyzer with a resolution of about ±80H2. Regarding 2, [,; 2-( is always changed every time the machining conditions are selected, so perform calculation control of [.-± (however, the sum of the period T, sub-time, and 4 times). There is a need.

Now, the output S, 4 will be explained in more detail using the detailed explanatory diagram of the level comparator 6J in FIG. 4.

The output of the low frequency amplification type 55 is an analog switch 62.63
Therefore, the comparators 64 and 65 are not connected to each other except at the timing of the 10th judgment and the 10th judgment. Then, at the f0 determination timing, the spectrum amplitude ■.

is larger than Vl, the output of the comparator 64 becomes l'',
A N I) Game 1・66 through 17-(Counter 6
Count 7! In addition, at the timing of detecting defects, V0 is greater than V2 (Aroto, comparator 6
The output of 5 becomes 1'', and the counter 67 is reset via A'ND game 1.68.
7, the content increases when the spectral amplitude is large at the fO timing, and when the 1H timing angle (0) Vo is large, the content increases! Immediately, the counter contents become zero. , 1-1, if there is a high frequency component, it is zero, [. If the component is large, the state of increase will be repeated, so we will observe the analog voltage ■. using the I)/A converter 4() to measure the content of this force.
, it should be possible to determine whether the condition of the gap between the poles is good or bad. If vo increases and vo becomes large -C arc], it means that an abnormal discharge is approaching.For example, if the sludge in the gap between the electrodes is twisted due to the accumulation of machining powder, or the abnormal arc is caused by an addition of 1g1
Problems such as carbon formation due to thermal decomposition of L&I 6, or a part of the electrode being damaged 17 and its fragments existing in the interelectrode gap 20 can be easily detected.

However, if it is for a short period of time (7 times), the inter-electrode gap condition (,1 is constantly changing, and for a short time, the condition of the inter-electrode gap (■) in 011 is present), but it cannot necessarily be determined that the inter-electrode gap condition is bad. It is necessary to detect whether the output vo of the digital analog converter 40 is greater than or equal to a predetermined value and continues for a certain period of time to determine whether the state of the gap between the electrodes is good or bad.

The voltage comparator 148 in FIG. Ana v
Output V of 1G conversion domain 40. is a predetermined value V, - it is determined whether the size is small or large. ■. 〉■, Niroto, voltage comparison tt!
The output of i 148 becomes negative, and the switching toranosk +52 is placed in the A] state (this 4
reactor. This): For measuring time: 1 point! The sensor 154 is charged via a resistor 156, and the voltage V across the sensor 154 is given by the following equation: /l
! l,, l'z l-L tl,, anti-156 Ji
(Anti-I'tC contains 154 yen of Konodenzu.

1 is a time period.The voltage across the capacitor 154 is compared with the reference voltage by the voltage comparator 158. During the period 'jl>v21, the output of the voltage comparator 158 is negative.

When the state of 〉■, 1 continues for a predetermined time and becomes Vjl〉■21, the output of the voltage comparator 158 becomes negative, and the light emitting diode A
-1j I 60 to 11 (turn on via resistor 162 -
(Displays the occurrence of an abnormality in the gap between the poles - 4).

Switches 1 and 4 are used to judge the gap state between poles only as a function of time, or to use the output v of digital analog converter 4 ().
It is a function of the product of the magnitude of 0 and time. "Add"
For example, when machining cemented carbide, cracks due to arcing or chipping of kunokusten occur instantaneously (in this case,
When the switch 164 is turned to the contact 1648 side in the illustrated example, the occurrence of an abnormality in the pole gap condition is changed to 1.
71.
If the charging current of the condenser 154 increases, t-near! This is because the voltage V, 1 across 1540 reaches the reference voltage 21.

Also, the output of ``Second Note ■. By observing directly with a voltmeter, it can be used as a monitor for the gap between the electrodes.

In the second embodiment, a first-order delay circuit consisting of a condescending circuit 154 and a resistor 156 is used on the time side when the inter-electrode condition deteriorates, but in order to make the time measurement more accurate, It is impossible to implement it by providing an accurate integration circuit using an operational amplifier 2g. Since it is possible to accurately detect the quality of the gap between the poles, additional
Operation 1: The effect of being able to prevent processing failures is obtained.

[Brief explanation of drawings]

Fig. 1 shows a conventional electric discharge machining device; Fig. 2 is an explanatory diagram of the principle according to the present invention; Fig. 3 is a frequency diagram; 10 is an electrode; 4 is a liquid injector; 18 is an electrode; The processing power source 67 is an abnormality detection counter. Note that the same arrows in the figures indicate the same or equivalent parts. Agent Akira Sumono

Claims (1)

[Claims] In an electric discharge machining device that machining the workpiece by generating an electric discharge in the gap between the electrodes, the electrode and the corrugated workpiece face each other with an insulating machining liquid interposed therebetween. Detecting means for detecting the distribution of frequency components in the electrical signal in the gap between the poles of an object F, and detecting means for detecting the distribution of frequency components in the electrical signal at the gap between the poles of the -1
- An output + of the comparing means is provided with means for determining the gap state of the electrodes by cutting off the gap state of the gap 17i7 and outputting a signal. On electrical equipment