JPH0761571B2 - Discharge classifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to an electric discharge classification device for classifying electric discharges generated in electric discharge applied equipment such as 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 explained by arranging wire electrodes at predetermined intervals with respect to a workpiece. 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, electric discharge is generated between the wire electrode and the workpiece. However, the workpiece is processed by this discharge energy.

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, the oscilloscope displays, for example, the waveforms of the discharge voltage and the discharge current between the wire electrode and the workpiece, and the discharge state is judged from these discharge voltage and 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.

That is all.

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,
The waveforms of the discharge voltage and the discharge current displayed on the oscilloscope are difficult to understand at any time, 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. With the other method, each manufacturer takes measures to avoid abnormalities and prevents various types of wire breakage, but on the contrary, it is not possible to achieve the highest efficiency machining, for example, the efficiency is always 60 to 70%. It lacks accuracy in detecting the processing state. In addition, the discharge voltage and discharge current detected by the methods and are average values,
Only the short circuit between the workpiece and the wire electrode can be detected from the discharge voltage and the discharge current. However, in the discharge of the actual discharge, the machining waste exists between the work piece and the wire electrode without being removed, and the discharge state changes depending on the amount of this machining waste. It is necessary to analyze the state. However, in each of the above methods, it is difficult to analyze the discharge state in detail.

(Problems to be Solved by the Invention) As described above, it is difficult to analyze the discharge state in detail.

Therefore, an object of the present invention is to provide a discharge classification device that can classify discharge states and analyze them in detail.

[Configuration of the Invention] (Means for Solving the Problem) The present invention provides a detector for detecting a discharge voltage and a discharge current between a workpiece and a discharge electrode, and a detection signal from the detector to a predetermined value. Signal sampling means for digitally converting and capturing over the signal sampling period, and discharge excluding no discharge in which discharge current does not occur despite voltage application based on the discharge voltage detection signal and the discharge current detection signal sampled by the signal sampling means Discharge data creating means for creating discharge voltage data for each occurrence, comparing the discharge voltage data created by the discharge data creating means with a preset discharge limit voltage, and abnormal discharge data based on the comparison result. Abnormality classification means for classifying into non-abnormal discharge data, and a histogram is created for the non-abnormal discharge data classified by the abnormal discharge classification means. A discharge classifying device, comprising: normal discharge data and normal discharge data, which is classified into normal discharge data and transient discharge data having different distribution modes on the low voltage side of the normal discharge data, based on the frequency distribution of the generated histogram. .

Further, the present invention provides a detector for detecting a discharge voltage and a discharge current between a work piece and a discharge electrode, and a signal sampling means for digitally capturing a detection signal from the detector for a predetermined signal sampling period. And a discharge for generating discharge voltage peak value data for each discharge occurrence excluding no discharge in which a discharge current does not occur in spite of voltage application based on the discharge voltage detection signal and the discharge current detection signal sampled by the signal sampling means. A histogram is created for the discharge current peak value data created by the data creating means and the discharge data creating means, and the normal discharge data and the low current peak value side of the normal discharge data are based on the frequency distribution of the created histogram. The transient discharge data exhibiting different distribution modes and different distribution modes on the low current peak side of the transient discharge data. A discharge classifier consisting comprises a classification means for classifying the abnormal discharge data.

(Operation) With the provision of such means, when either or both of the discharge voltage and the discharge current of the discharge application device are detected, this detection signal is digitally converted at each predetermined interval of infringement sampling period. Are taken in and created as discharge data such as discharge voltage. Then, if the discharge voltage from the discharge data is below a predetermined level by the abnormality classification means, the discharge state of this discharge voltage is classified as abnormal,
Further, a histogram of each parameter is created from the remaining discharge data excluding the data classified as abnormal by the normal classification means, and the discharge state is classified into at least two according to the frequency.

Further, by providing the above means, a histogram of the current peak is created from the discharge data, and the discharge state is classified from the frequency distribution of this histogram.

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

FIG. 1 is an overall configuration diagram of a discharge classification device. The workpiece 2 is infiltrated into the processing tank 1. This work piece 2
Wire electrodes 3 are arranged at predetermined intervals.
The wire electrode 3 is supported by the upper wire guide body 4 and a lower wire guide body (not shown). A DC power supply 6 is connected between the work piece 2 and the wire electrode 3 via a discharge control circuit 5 to form a discharge circuit. In this case, the DC power supply 6 has its positive electrode connected to the workpiece 2. A voltage detector 7 is connected in parallel to the DC power supply 6 and a current detector 8 is connected in series to the DC power supply 6 in this discharge circuit.

On the other hand, 10 is the sorting apparatus body, and this sorting apparatus body 10
Are provided with attenuators (ATT) 11 and 12, and the voltage detector 7 is connected to one attenuator 11 and the current detector 8 is connected to the other attenuator 12. Attenuators 11 and 12 are connected to respective A / D (analog / digital) converters 13 and 14 each having a built-in memory, and these A / D converters 13 and 14 are connected to a CPU (central processing unit) via a bus 15. Device) 16 is connected. This CPU16 has a bus 15
Through the timing controller 17, RAM (random
An access memory) 18, a ROM (read only memory) 19 and a display drive unit 20 are connected. The timing controller 17 controls the signal acquisition timing in the A / D converters 13 and 14. Further, a display device 21 is connected to the display drive section 20 to drive the display device 21 for display. The ROM 19 stores a discharge analysis program that determines discharge start time, discharge end time, current peak value, pulse interval, and other discharge data from the applied voltage and discharge current that are fetched, and determines the quality of the discharge from this discharge data. Has been done. The ROM 19 also stores a signal sampling timing program for the A / D converters 13 and 14 in the timing controller 17. However, the A / D converters 13 and 14 according to the signal sampling timing program digitally convert the voltage detection signal and the current detection signal into 8 bits at the same time, for example, at every xns in the signal sampling period at a constant interval, and 1
For example, data of 1024 to 65536B will be collected in the signal collection period of once. The interval between the signal acquisition periods is set to a constant period ΔH. However, each A / D converter 13,1
4, the CPU 16, the timing controller 17, and the ROM 19 constitute a signal sampling means. The ROM 19 also stores a discharge data creation program, an abnormal classification program, and a normal classification program. As a result, the above CPU16
As shown in FIG. 2, signal sampling means 16-1, discharge data creating means 16-2, abnormality classifying means 16-3 and normal classifying means
It has each function of 16-4. The signal sampling means 16-1 has a part of the function of the means 16-1 as described above. The discharge data creating means 16-2 has a function of creating discharge data consisting of parameters such as discharge voltage and discharge current in each discharge from the digital voltage detection signal and the digital current detection signal sampled by the signal sampling means. Further, the abnormality classifying means 16-3 has a function of classifying that the discharge state at this discharge voltage is abnormal if the discharge voltage created by the discharge data creating means 16-2 is equal to or lower than the discharge limit voltage of a predetermined level. It is a thing. Then, the normal classification means 16-4 removes the data classified as abnormal by the abnormality classification means 16-3 from the discharge data created by the discharge data creation means 16-2 and creates a histogram of the discharge voltage from the remaining discharge data. Based on the frequency, it has a function of classifying into an electric discharge state when the machining waste between the workpiece 2 and the wire electrode 3 is sufficiently cleaned and an electric discharge state when the machining waste is not sufficiently cleaned. is there.

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

A DC voltage is applied between the work piece 2 and the wire electrode 3 from the DC power supply 6 through the discharge control circuit 5, and when the gap amount between the work piece 2 and the wire electrode 3 reaches a predetermined amount in this state, the work piece is processed. A discharge is generated between the object 2 and the wire electrode 3. The workpiece 2 is processed by the energy of this discharge.

In this state, the voltage detector 7 detects the discharge voltage between the workpiece 2 and the wire electrode 3 and outputs the voltage detection signal,
The current detector 8 detects the discharge current flowing from the work piece 2 to the wire electrode 3 and outputs the current detection signal. These voltage detection signal and current detection signal are attenuated to levels that can be easily processed by the attenuators 11 and 12, respectively, and then the A / D converter 1
Type in 3,14. At this time, the A / D converters 13 and 14 are both controlled by the timing controller 17 to digitally convert the voltage detection signal and the current detection signal, respectively.
That is, the A / D converters 13 and 14 simultaneously digitally convert the voltage detection signal and the current detection signal into 8-bit signals, for example, every xns in each signal sampling period at constant intervals ΔH. As a result, the data of B is taken in during _one signal sampling period, for example, the signal sampling period S ₁ .
The digital voltage detection signal and the digital current signal thus acquired in one signal sampling period are temporarily stored in the memories in the respective A / D converters 13 and 14, and after the lapse of each signal sampling period, the CPU 16 It is moved to RAM 18 and stored.

In this way, the digital voltage detection signal and the digital current signal are fetched and stored in the RAM 18, and, for example, when the signal sampling period of 10 times ends, the discharge data creating means 16 of the CPU 16
-2 obtains respective waveforms of the discharge voltage and the discharge current as shown in FIG. 3 from the respective digital voltage detection signals and the digital current signals, and the generation numbers “1”, “2”, ... N "is added. However, when no voltage is applied and no discharge is generated between the workpiece 2 and the wire electrode 3 and no discharge current flows, no generation number is given. That is, the numbers are attached only when the discharge occurs. Then, the CPU 16 determines from these waveforms that discharge start a1, a2 ... an and discharge end b1, in each discharge.
b2 ... bn, discharge voltage c1, c2 ... cn, current peak d1, d2 ... dn, current pulse width e1, e2 ... en, discharge energy f1, f2, fn, pulse interval g1, g2 ... gn, etc. The discharge data D is obtained and tabulated and stored in the RAM 18.

Next, the abnormality classifying means 16-3 of the CPU 16 compares the preset discharge limit voltage with each discharge voltage c1, c2 ... Cn, and discharges a discharge voltage lower than the discharge limit voltage, for example, c2, which is an abnormal discharge arc. Detect as discharge pulse and short circuit. When the abnormal discharge is detected in this way, each data of the discharge start a2, the discharge end b2, the discharge voltage c2, and the current peak value d2 of the occurrence number "2" of this abnormal discharge c2 is deleted from the table. In this case, the occurrence number “2” is moved to the abnormal discharge table formed in the RAM 18. As a result, abnormal discharge (arc discharge pulse) and normal discharge are classified.

Next, the normal classification means 16-4 of the CPU 16 extracts the discharge voltages c1, c3, c4 ... cn-1, cn from the discharge data D in which the abnormal discharge has been erased, and creates the histogram of the discharge voltage shown in FIG. .
Two normal distributions Q ₁ and Q ₂ appear in the histogram created in this way. Here, the normal distribution Q ₁ is the workpiece 2
Between the wire electrode 3 and the wire electrode 3 shows the discharge voltage in the state where the flow of the working liquid has sufficiently cleaned and the processing dust has been removed. In this state, the discharge voltage shows the normal distribution Q ₁ A slight residual machining waste between the work piece 2 and the wire electrode 3 causes variations in the discharge resistance value and a change in the gap amount between the work piece 2 and the wire electrode 3 due to vibration of the wire electrode 3 and the like. to cause. On the other hand, the normal distribution Q ₂ is, for example, when the machining speed is increased from the electric discharge machining with the normal distribution Q ₁ , and in this case, a considerable amount of machining waste remains between the workpiece 2 and the wire electrode 3. The resistance value between the gaps becomes small due to the machining waste, and even if the discharge voltage is low, a transient discharge is generated. Therefore, the normal classification means 16-4 classifies clean discharges into true normal discharges and transient discharges.

As described above, in the above-described embodiment, the detection signals of the discharge voltage and the discharge current are sampled to create the discharge data D, and if the discharge voltage is equal to or lower than the discharge limit voltage, the discharge state of the discharge voltage is Since the discharge is classified as abnormal, it is possible to quantitatively determine whether the discharge is normal or abnormal, that is, whether the discharge is an arc discharge pulse or a short circuit.

Furthermore, by classifying the discharge data that was not determined to be abnormal discharge into normal discharge data and transient discharge data, conventionally, the transient discharge state that is a caution state from the discharge data determined to be normal discharge The discharge state determination accuracy is significantly improved.

That is, in general, the normal discharge means a state in which the next discharge occurs after the insulating state is sufficiently recovered and the processing waste is almost completely discharged. Since this normal discharge is not greatly affected by the atmosphere of the discharge gap (the discharge state of the processing waste), it is possible to form the discharge in the form closest to the set conditions.

On the other hand, in the transient discharge, when a part of the machining waste remains, the insulation is not completely restored, so the specific resistance becomes low, and the next discharge occurs at low current and low voltage. Refers to the discharged state.

This transient discharge is an electrical continuity (arc discharge or short circuit)
Unlike the abnormal electric discharge that is in a non-machined state, electric discharge machining is performed, but its machining capacity is small. The occurrence of such a transient discharge has a high risk of disconnection of the wire electrode 3 and requires a change in processing conditions.

Therefore, as in this embodiment, by distinguishing between the normal discharge and the transient discharge state and determining the discharge state, it is possible to prevent the worst situation such as disconnection of the wire electrode 3 in advance. It can contribute to the improvement of the electric discharge machining efficiency and the electric discharge machining accuracy.

Next, a second embodiment of the present invention will be described. Since the hardware configuration of the embodiment is the same as that of the apparatus shown in FIG. 1, only the different functional parts will be described using the reference numerals in the figure.
The ROM 19 stores a signal collection program, a discharge data creation program, and a classification program. As a result, the CPU 16 causes the signal sampling means 16-1, as shown in FIG.
The discharge data creating means 16-2 and the classification means 16-5 have respective functions. Here, the classifying means 16-5 creates a histogram of current peaks from the discharge data D created by the discharge data creating means 16-2, and determines the discharge state to be abnormal, transient or true normal from the frequency distribution of this histogram. It has a classification function.

With such a configuration, the classifying means 16-5 creates a histogram of the current peaks d1, d2, d3, ... Dn from the discharge data D. FIGS. 6 and 7 are histograms of current peaks. In FIG. 6, two normal distributions appear, and in FIG. 7, three normal distributions appear. Explaining the classification of discharges in the histogram of FIG. 6, the classifying means 16-5 sets a threshold S ₁ which passes through the inflection point of the histogram, and the threshold S ₁ is used as a boundary to divide the histogram into two groups.
Divide into P ₁ and P ₂ . Then, the classification means 16-5 makes the histogram group P ₁ a true normal discharge and
Classify P ₂ as a transient discharge. Explaining the classification of discharges in the histogram of FIG. 7, the classification means 16-5 sets the thresholds S ₂ and S ₃ passing through the respective inflection points of the histogram, and these thresholds S ₂ and S ₃ are set as boundaries. The histogram is divided into 3 groups P ₁ , P ₂ and P ₃ . And the classification means 1
6-5, similarly to the above, makes the histogram group P ₁ a true normal discharge and the histogram group P ₂ a transient discharge,
Further, the histogram group P ₃ is classified as abnormal discharge (arc discharge pulse or short circuit).

As described above, in the second embodiment, the histogram of the current peak is created from the discharge data D, and the discharge state is classified into the true normal discharge, the transient discharge, and the abnormal discharge based on the frequency distribution. The same effect as the first embodiment can be obtained. Moreover, since the discharge current comprehensively reflects the machining conditions and machining states and does not include unstable elements and noise, the reliability of the discharge classification results is high.

The present invention is not limited to the above-mentioned embodiments, and may be modified without departing from the spirit of the invention. For example, in the first embodiment, the abnormal discharge and the normal discharge may be classified by creating a histogram of the discharge energies f1, f2 ... Fn and classifying from the normal distribution. In addition, this equipment is not limited to wire electric discharge machining equipment, but can also be used for die-sinking electric discharge machining, electrolytic machining, and by changing the sampling range of voltage and current signals, welding machines, laser applied equipment, lighting equipment, sputtering equipment, PVD and CVD equipment. 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 The present invention can improve the accuracy of discharge state determination by classifying the discharge state into normal discharge, transient discharge, and abnormal discharge. In other words, normal discharge means that after the insulation state has been sufficiently restored and machining waste has been almost completely discharged,
The state in which the next discharge occurs. This normal discharge is
Since the atmosphere in the discharge gap (the discharge state of the processing waste) is not significantly affected, it is possible to form the discharge in the form closest to the set conditions. On the other hand, in the transient discharge, when a part of the machining waste remains, the insulation is not completely restored, so the specific resistance becomes low, and the next discharge occurs at low current and low voltage. Refers to the discharged state. This transient electric discharge is different from abnormal electric discharge (arc discharge or short circuit) in which electrical processing (arc discharge or short circuit) is impossible, but electrical discharge machining is performed, but its machining capacity is small and the risk of wire electrode disconnection is high. Need to change the conditions.

Therefore, as in the present invention, by determining the discharge state by distinguishing between the normal discharge state and the transient discharge state, it is possible to prevent the worst situation such as wire electrode disconnection. It can contribute to improvement of efficiency and electric discharge machining accuracy.

[Brief description of drawings]

1 to 4 show the first embodiment of the discharge classification device according to the present invention.
FIG. 1 is a diagram for explaining an embodiment, FIG. 1 is a configuration diagram,
FIG. 2 is a functional block diagram, FIG. 3 is a waveform diagram of discharge voltage and discharge current, FIG. 4 is a diagram for explaining the classification action of discharge, and FIG. 5 is a function of the second embodiment of the device of the present invention. Block diagrams, FIG. 6 and FIG. 7 are diagrams for explaining the classification function of discharges. 1 ... Machining tank, 2 ... Workpiece, 3 ... Wire electrode, 4
...... Upper wire guide body, 5 …… Discharge control circuit, 6 ……
DC power supply, 7 ... voltage detector, 8 ... current detector, 10 ...
… Monitor device main body, 11,12 …… Attenuator, 13,14 ……
A / D converter, 15 ... Bus, 16 ... CPU, 16-1 ... Signal sampling means, 16-2 ... Discharge data creating means, 16-3 ... Abnormality classification means, 16-4 ... Normal Classification means, 16-5 ... Classification means, 17 ... Timing controller, 18 ... RAM, 19
...... ROM, 20 …… Display drive, 21 …… Display.

Claims (2)

[Claims] 1. An electric discharge machining state comprising the following constitutions (a) to (e), wherein a voltage is periodically applied between a workpiece and an electric discharge electrode to perform electric discharge machining of the workpiece. Discharge classification device to classify. (A) A detector that detects a discharge voltage and a discharge current between the workpiece and the discharge electrode. (B) Signal sampling means for digitally capturing the detection signal from the detector for a predetermined signal sampling period. (C) Discharge data for creating discharge voltage data for each discharge occurrence excluding no discharge in which no discharge current is generated despite voltage application based on the discharge voltage detection signal and the discharge current detection signal sampled by the signal sampling means Means of creation. (D) An abnormality classifying unit that compares the discharge voltage data created by the discharge data creating unit with a preset discharge limit voltage, and classifies the discharge voltage data into abnormal discharge data and non-abnormal discharge data based on the comparison result. (E) A histogram is created for non-abnormal discharge data classified by the abnormal discharge classification means, and normal discharge data and different distribution modes on the low voltage side of the normal discharge data are set based on the created histogram frequency distribution. Normal classification means for classifying into transient discharge data to be presented. 2. An electric discharge machining state comprising the following constitutions (a) to (d), wherein a voltage is periodically applied between a workpiece and an electric discharge electrode to discharge the workpiece. Discharge classification device to classify. (A) A detector that detects a discharge voltage and a discharge current between the workpiece and the discharge electrode. (B) Signal sampling means for digitally capturing the detection signal from the detector for a predetermined signal sampling period. (C) Based on the discharge voltage detection signal and the discharge current detection signal sampled by the signal sampling means, discharge current peak value data is created for each discharge occurrence except no discharge in which no discharge current is generated despite voltage application. Means for creating discharge data. (D) A histogram is created for the discharge current peak value data created by the discharge data creating means, and normal discharge data is created based on the frequency distribution of the created histogram.
Classification that is classified into transient discharge data exhibiting different distribution modes on the low current peak value side of this normal discharge data and abnormal discharge data exhibiting different distribution modes on the low current peak value current peak value side of this transient discharge data means.