JPH0716820B2 - Discharge pulse parameter detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a discharge pulse parameter detection method for detecting a discharge pulse parameter of electric discharge machining.

(Prior Art) For example, electric discharge machining includes wire electric discharge machining and die-sinking electric discharge machining. Of these, for example, wire electric discharge machining will be described. The workpiece and the wire electrode are soaked into the machining tank, and a DC voltage is applied between the workpiece and the wire electrode in this state. Then, for example, when the wire electrode is brought close to the workpiece and the gap amount becomes a predetermined amount, pulse discharge is generated between the wire electrode and the workpiece.
However, the work piece is processed by the energy of the pulse discharge.

In such wire electric discharge machining, the quality of the machining state is judged. This judgment is made based on whether the electric discharge state is normal or abnormal. This judgment is made by the following method. . That is, a worker visually checks the discharge column and judges the discharge state by experience and intuition based on the brightness of the discharge column.

The worker hears the sound of the discharge, and judges the discharge state from the sound of the discharge by experience and intuition.

If the wire electric discharge machine is equipped with an oscilloscope, for example, the oscilloscope displays the waveforms of the discharge voltage and the discharge current between the wire electrode and the workpiece, and the discharge state is judged from the discharge voltage and the discharge current. .

If a standard for the quality of the discharge state is set in advance in the wire electric discharge machine, the discharge state is determined according to this standard.

However, among the above methods, the method and the method do not quantitatively determine the discharge state, but the determination results vary. In the method (1), the frequency band of the oscilloscope is slower than that of discharging, and the discharging voltage and discharging current cannot be displayed in real time. Furthermore, since the occurrence of discharge is random and the discharge voltage and discharge current are not retained,
It is difficult to know when the discharge voltage and discharge current displayed on the oscilloscope are waveforms, and it is difficult to quantitatively judge from the waveforms. In the method (1), the quality standard is set by each manufacturer, for example, and cannot be applied to all discharge state determinations.

When performing wire electric discharge machining, a DC voltage is applied between the workpiece and the wire electrode. The power supply for applying the DC voltage is roughly classified into a synchronous type and an asynchronous type. However, since the waveforms of the discharge voltage and the discharge current differ depending on the power source type, it is necessary to change the detection method depending on the power source type. However, in the above method, the power source type is not taken into consideration for detection, and the reliability is low.

(Problems to be Solved by the Invention) As described above, the reliability of the detection of the discharge voltage and the discharge current is low depending on the power source type.

Therefore, it is an object of the present invention to provide a discharge pulse parameter detection method capable of accurately detecting a discharge pulse parameter of a discharge voltage or a discharge current according to a power source type.

[Constitution of the Invention] The present invention relates to a discharge voltage when a workpiece is processed by applying a voltage between the workpiece and an electrode to generate a pulse discharge between the workpiece and the electrode. In a discharge pulse parameter detection method for detecting a discharge pulse parameter, the type of a power supply that applies a voltage between a workpiece and an electrode is identified as two types, a natural discharge type or a constant energy supply type,
Among them, in the case of the natural discharge type power supply, at least the discharge voltage value at the time of starting the discharge is detected as the discharge pulse parameter, and in the case of the constant energy supply type power supply, at least when the minute discharge occurs before the main discharge occurs. A discharge pulse parameter detection method for achieving the above object by detecting a discharge voltage value as a discharge pulse parameter.

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

FIG. 1 is an overall configuration diagram of a wire machining discharge device to which a discharge pulse parameter detection method is applied. The workpiece 2 is infiltrated into the processing tank 1. Wire electrodes 3 are arranged on the workpiece 2 at predetermined intervals. In addition,
The wire electrode 3 is supported by an upper wire guide body 4 and a lower wire guide body (not shown). A power source 5 is connected between the work piece 2 and the wire electrode 3. In this case, the power source 5 connects the positive electrode to the workpiece 2. Further, the power source 5 is of a synchronous type or an asynchronous type. For example, in the asynchronous type, a no-load voltage Vl is applied between the work piece 2 and the wire electrode 3 to generate a minute discharge due to dielectric breakdown. Immediately after the minute discharge is detected, a voltage is applied to control the generation of the main discharge between the workpiece 2 and the wire electrode 3. A voltage detector 6 is connected in parallel to the power source 5 and a current detector 7 is connected in series.

On the other hand, the electric discharge analysis apparatus main body 10 has a function of analyzing the pulse discharge generated between the work piece 2 and the wire electrode 3, and the work piece 2 and the wire electrode 3 are detected when the pulse discharge is detected. The type of the power supply 5 which applies a voltage between the two is classified into a natural discharge type and a constant energy supply type, and in the case of the natural discharge type power supply 5, the discharge voltage value and the current when the discharge starts The peak value, the current pulse width, etc. are detected as the discharge pulse parameters, and in the case of the constant energy supply type power source 5, the discharge voltage value, the current peak value, the current pulse width, etc. at the time of the occurrence of the minute discharge before the main discharge occurs It has a function of detecting as a discharge pulse parameter. Explaining the configuration concretely, attenuators (ATT) 11 and 12 are provided, one of the attenuators 11 and 12 is connected to the voltage detector 6, and the other attenuator 12 is connected to the current detector 7. It is connected. These attenuators 11 and 12 each have a built-in memory.
/ D (analog / digital) converters 13 and 14 are connected,
These A / D converters 13 and 14 are connected to a CPU (central processing unit) 16 via a bus 15. Timing controller 17, RAM (random access memory) 18, ROM (read only memory) 1 are connected to this CPU 16 via bus 15.
9, a display drive unit 20, a printer drive unit 21, and an input unit 22 are connected. Timing controller 17 is A / D converter 1
It controls the signal acquisition timing in 3 and 14. A display device 23 such as a CRT display is connected to the display drive unit 20, and a printer 24 is connected to the printer drive unit 21.

The discharge parameter detection program is stored in the ROM 19, and by executing this program, the CPU 1
6 identifies the type of the power supply 5 as a natural discharge type or a constant energy supply type. Of these, in the case of the natural discharge type power supply 5, the discharge voltage value, the current peak value, and the power supply pulse when the discharge starts. The width and the like are detected as discharge pulse parameters, and in the case of the constant energy supply type power supply 5, the discharge voltage value, the current peak value, the current pulse width, etc. at the time of the occurrence of the minute discharge before the main discharge is detected as the discharge pulse parameter. It has a function to do. Further, the ROM 19 stores a discharge data creation program, a discharge classification program, a discharge analysis program, and the like.

Next, the operation of the apparatus configured as described above will be described with reference to FIG.

When a DC voltage is applied between the work piece 2 and the wire electrode 3 from the power source 6 and the gap amount between the work piece 2 and the wire electrode 3 reaches a predetermined amount in this state, the work piece 2 and the wire electrode 3 A pulse discharge is generated between and, and the workpiece 2 is processed by the energy of this pulse discharge.

In this state, the voltage detector 6 detects the pulse discharge voltage between the workpiece 2 and the wire electrode 3 and outputs the voltage detection signal, and the current detector 7 outputs the voltage from the workpiece 2 to the wire electrode 3. The flowing pulse discharge current is detected and the current detection signal is output. The voltage detection signal and the current detection signal are respectively attenuated to a level that can be easily processed by the attenuators 11 and 12 and input to the A / D converters 13 and 14. At this time, each A / D converter 1
Both 3 and 14 are controlled by the timing controller 17 to digitally convert the voltage detection signal and the current detection signal, respectively. The digital voltage detection signal and the digital current signal are temporarily stored in the memories in the A / D converters 13 and 14, respectively, and then transferred to the RAM 18 by the CPU 16 and stored therein.

When the digital voltage detection signal and the digital current signal are stored in the RAM 18 in this way, the CPU 16 obtains the waveforms of the discharge voltage and the discharge current from the digital voltage detection signal and the digital current signal, respectively. Start, finish, discharge peak value, current pulse width, etc. By the way, in this case, the CPU 16 recognizes through the input unit 22 whether the type of the power source 5 is the natural discharge type or the constant energy supply type.

Here, a case where the CPU 16 recognizes the power supply 5 as a spontaneous discharge type such as an asynchronous capacitor power supply will be described. The CPU 16 obtains respective waveforms of the discharge voltage and the discharge current as shown in FIG. 2 from the digital voltage detection signal and the digital current signal stored in the RAM 18. However, CP
U16 is a discharge voltage value V ₁ , V ₂ , V ₃ ..., Current peak value I _P1 , I _P2 , when the discharge is started from these discharge voltage and discharge current.
I _P3 …, current pulse width Pd ₁ , Pd ₂ , Pd ₃ …, further discharge start,
Each discharge pulse parameter such as discharge end, discharge energy, pulse interval, etc. is obtained. Then, the CPU 16 creates a table of these discharge pulse parameters as discharge data and RA
Remember in M18.

When the CPU 16 recognizes the power supply 5 as a constant energy supply type such as an asynchronous constant voltage application type transistor power supply, the digital voltage detection signal and the digital current signal stored in the RAM 18 are discharged as shown in FIG. Obtain each waveform of voltage and discharge current. By the way, when the power source 5 is of a constant energy supply type, the discharge between the work piece 2 and the wire electrode 3 causes a small discharge first, and then the main discharge of the processing. However, in the waveform shown in FIG. 3, A is a minute discharge period, B is a main discharge charge period, C is a main discharge period, D is a rest period, and E is a next minute discharge period.
We show Va, discharge voltage Vb is small discharge, V _S is a discharge voltage value, I _P a, I _P b is the current peak value, Pda, Pdb is the current pulse width. Therefore, the discharge voltages Va and Vb during the minute discharge are the breakdown voltage between the workpiece 2 and the wire electrode 3. Then, the discharge voltage value V _S of the main discharge and the current peak value I
_{Although P} a and I _P b do not change under the control of the power supply 5, the discharge voltages Va and Vb of the minute discharge change depending on the processing state. Therefore, the discharge voltage during the main discharge is used by detecting these discharge voltages Va and Vb. Therefore, CPU 16 is a discharge voltage value Va which definitive when micro discharge occurs, Vb, ..., current peak value _{I P a, I P b,} ..., the current pulse width Pda, Pdb, ..., Furthermore discharge start, completion of discharge, discharge energy, Each discharge pulse parameter such as the pulse interval is obtained, and these discharge pulse parameters are tabulated as discharge data and stored in the RAM 18.

When the discharge data is obtained in this way, the CPU 16 analyzes the discharge state. For example, the discharge classifying unit of the CPU 16 compares the preset discharge limit voltage with each discharge voltage, for example, the discharge voltage values V ₁ , V ₂ , ... (See FIG. ₂ in the case of a natural discharge type) (see FIG. 2). Discharge voltage value whose level is lower than the voltage
Detecting the V ₂ as arc discharge pulses and short is abnormal discharge. When the abnormal discharge is detected in this way, each data of the abnormal discharge is deleted from the table. Next, the discharge classification means extracts discharge voltage values V ₁ , V ₃ , ... From the discharge data in which the abnormal discharge has been erased, and creates a histogram of the discharge voltage values. Two histogram groups appear in the histogram created in this way, and one of the histogram groups is sufficiently cleaned between the workpiece 2 and the wire electrode 3 due to the flow of the machining liquid to generate machining waste. The normal discharge voltage in the removed state is shown, and in the other histogram group, a considerable amount of machining waste remains between the work piece 2 and the wire electrode 3, and the resistance value between the gaps is small due to this machining waste. Therefore, even if the discharge voltage is low, a transient discharge in which discharge is occurring is shown.

Next, the analysis calculation means of the CPU 16 calculates efficiency and stability. For example, the efficiency calculating operation will be described. The analysis calculating means calculates the total period H ₀ of the signal sampling periods of the digital voltage detection signal and the digital current signal and the pulse generation number E of the total period, and calculates the pulse generation interval T from them. To do. That is, T = H ₀ / E, and the efficiency Q is calculated by the following equation where α is a constant.

Q = α / T When the efficiency Q is calculated in this way, the analysis calculation means sends the efficiency Q to the display drive unit 20 to display it on the display device 23.
Further, the analysis calculation means 16-7 obtains the stability and the surface roughness of the workpiece 2.

As described above, in the above embodiment, the type of the power source 5 is classified into two types, that is, the natural discharge type and the constant energy supply type,
Among them, in the case of the natural discharge type power supply 5, the discharge voltage value, the current peak value, the current pulse width, etc. at the time when the discharge is started are detected as the discharge pulse parameters, and in the case of the constant energy supply type power supply 5, the main discharge is performed. Since the discharge voltage value, the current peak value, the current pulse width, etc. at the time of the occurrence of the minute discharge before the occurrence are detected as the discharge pulse parameters, the power source 5 is either the natural discharge type or the constant energy supply type. However, discharge pulse parameters such as discharge voltage value and current peak value during discharge can be accurately detected. As a result, the machining discharge can be classified into normal discharge and transient discharge, and the efficiency and stability of the machining discharge can be accurately obtained.

The present invention is not limited to the above-described embodiment, and may be modified without departing from the spirit of the invention. For example, this equipment is not limited to wire electrical discharge machining equipment, but also die-sinking electrical discharge machining, electrolytic machining, and welding machines, laser applied equipment, lighting equipment, sputtering equipment, PVD and CVD by changing the sampling range of voltage and current signals. It can also be applied to electric discharge application equipment such as plasma processing equipment. Among them, the sputtering apparatus can adjust the flow rate of the discharge medium by detecting the discharge state.

[Effects of the Invention] As described in detail above, according to the present invention, the discharge pulse parameters such as the discharge voltage value and the current peak value can be accurately measured regardless of whether the power source is a natural discharge type or a constant energy supply type. It is possible to provide a discharge pulse parameter detection method that can detect the above.

[Brief description of drawings]

FIGS. 1 to 3 are views for explaining an embodiment in which the discharge pulse parameter detecting method according to the present invention is applied to a wire machining discharge device, and FIG. 1 is a configuration diagram and FIG. Is a waveform diagram when using a natural discharge type power supply, and FIG. 3 is a waveform diagram when using a constant energy supply type power supply. 1 ... Machining tank, 2 ... Workpiece, 3 ... Wire power supply, 4
...... Upper wire guide body, 5 …… Power supply, 6 …… Voltage detector, 7 …… Current detector, 10 …… Analysis device main body, 11, 12…
Attenuator, 13,14 A / D converter, 15 Bus, 16
...... CPU, 17 …… Timing controller, 18 …… RAM,
19 ... ROM, 20 ... display drive, 21 ... printer drive, 22 ... input, 23 ... display, 24 ... printer.

Claims (1)

[Claims] 1. A discharge pulse parameter such as a discharge voltage at the time of machining the workpiece by generating a pulse discharge between the workpiece and the electrode by applying a voltage between the workpiece and the electrode. In the discharge pulse parameter detection method for detecting the voltage, the type of the power supply that applies a voltage between the workpiece and the electrode is classified into two types, a natural discharge type and a constant energy supply type. In the case of the power supply of, at least the discharge voltage value when the discharge is started is detected as the discharge pulse parameter, and in the case of the constant energy supply type power supply, at least the discharge voltage value at the time of the occurrence of the minute discharge before the main discharge occurs. Is detected as the discharge pulse parameter.