JPH0710460B2 - Power supply evaluation device for electrical discharge machining - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a power supply evaluation apparatus in electric discharge machining for evaluating a power supply circuit used in wire electric discharge machining, for example.

(Prior Art) There are wire electric discharge machining, die-sinking electric discharge machining, etc. in the electric discharge machining. For example, in the case of the wire electric discharge machining, a wire electrode is arranged at a predetermined interval with respect to a workpiece. The workpiece and the wire electrode penetrate into the processing tank, and a DC voltage is applied between the workpiece and the wire electrode from the power supply circuit 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.

By the way, in such electric discharge machining, the discharge energy varies depending on the performance of the power supply circuit that applies a DC voltage between the workpiece and the wire electrode. For example, if the power supply circuit is composed of a plurality of transistors, a large discharge energy can be obtained if the ON timings of these transistors match, but a low discharge energy otherwise. When the discharge energy becomes low as described above, the processing accuracy is lowered and the processing efficiency is deteriorated. However, there is no technology for evaluating the performance of such a power supply circuit, and no consideration is given to the power supply circuit.

(Problems to be Solved by the Invention) As described above, there is no technique for evaluating the performance of a power supply circuit for electric discharge machining, and no consideration has been given to the power supply circuit. This is not limited to wire electrical discharge machining, and can be applied to other electrical discharge machining.

Therefore, an object of the present invention is to provide a power supply evaluation device in electric discharge machining, which can evaluate a power supply circuit for electric discharge machining.

[Structure of the Invention] (Means for Solving the Problems) The present invention relates to each switching of a power supply circuit that sequentially operates a plurality of switching elements connected in parallel to supply power between a workpiece and a discharge electrode. In a power supply evaluation device for electric discharge machining that evaluates the operation timing of elements, a discharge current detector that detects the discharge current that flows between the workpiece and the discharge electrode, and a current detection signal from this discharge current detector are received. The peak value of the discharge current is taken out, and a histogram creating means for creating a histogram for this discharge current peak value and a distribution value for the optimum value are obtained from the distribution state of the histogram of the discharge current peak value created by this histogram creating means, This variance value is compared with preset evaluation data, and based on the comparison result, each of the switches in the power supply circuit is compared. A power evaluation means for evaluating for operation timing of the switching element, a power supply evaluation device in the discharge machining to be achieved the above object comprises a.

(Operation) By providing such means, the discharge current flowing between the workpiece and the discharge electrode is detected by the discharge current detector, and the discharge current is received by the current detection signal from the discharge current detector. Is taken out and its histogram is created by the histogram creating means. Then, from the distribution state of the histogram of the discharge current peak value, the variance value for the mode value is obtained by the power supply evaluation means, the variance value and preset evaluation data are compared, and based on this comparison result. The operation timing of each switching element in the power supply circuit is evaluated.

(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 power supply evaluation device in electric discharge machining applied to wire electric discharge machining. The workpiece 2 is infiltrated into the processing tank 1. Wire electrodes 3 are arranged on the workpiece 2 at predetermined intervals. The wire electrode 3 is supported by an upper wire guide body and a lower wire guide body (not shown). A power supply circuit 4 is connected to the work piece 2 and the wire electrode 3.
The power supply circuit 4 is provided with a DC power supply 5, and the DC power supply 5 has a positive electrode connected to the workpiece 2 and a negative electrode connected to the wire electrode 3. A plurality of, for example, 40 NPN type transistors Q ₁ , Q ₂ ... Qn are connected between the negative electrode of the DC power source 5 and the wire electrode 3. More specifically, the emitters of the NPN transistors Q ₁ , Q _2, ... Qn are commonly connected to the negative electrode of the DC power supply 5, and the collectors are commonly connected to the wire electrode 3. The bases of the NPN transistors Q ₁ , Q _2, ... Qn are commonly connected to the base current supply circuit 6. This base current supply circuit 6 is for each NPN
The base currents of the same value are supplied to the respective bases of the type transistors Q ₁ , Q ₂ ... Qn.

A discharge current detector 7 is provided between the wire electrode 3 and the power supply circuit 4.
And a discharge voltage detector 8 is connected between the wire electrode 3 and the workpiece 2.

On the other hand, 10 is a power supply evaluation apparatus main body, and this power supply evaluation apparatus main body 10 is provided with attenuators (ATT) 11 and 12, and one attenuator 11 is connected to the discharge current detector 7 and the other attenuator 12 is connected. The discharge voltage detector 8 is connected to. 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 C
PU16 to the timing controller 17, RA via bus 15
M (random access memory) 18, ROM (read only memory) 19, display driver 20 and printer driver 21
Are connected.

The timing controller 17 controls the signal acquisition timing in the A / D converters 13 and 14. A CRT display 22 is connected to the display drive unit 20 to drive the display of the CRT display 22.
A printer 23 is connected to the printer 21 to perform a printing operation.

The ROM 19 stores a signal sampling timing program for the A / D converters 13 and 14 in the timing controller 17. However, according to this signal sampling timing program, the A / D converters 13 and 14 simultaneously digitally convert the discharge current detection signal and the discharge voltage detection signal into 8 bits, for example, every xns during the signal sampling period at a constant interval, and set 1 For example, data of 1024 to 65536B will be collected in the signal collection period of once. In addition, the interval of each signal acquisition period is set to a fixed period.

Further, the ROM 19 stores a discharge data creation program, a histogram creation program, and a power supply evaluation program. As a result, the CPU 16 has the respective functions of the signal sampling means 16-1, the discharge data creating means 16-2, the histogram creating means 16-3 and the power source evaluating means 16-4 as shown in FIG. 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 discharge current detection signal and the digital discharge voltage detection signal sampled by the signal sampling means. The histogram creating means 16-3 has a function of creating a histogram by reading the discharge current peak value from the discharge data created by the discharge data creating means 16-2.

The power supply evaluation means 16-4 extracts the discharge current that is not affected by the machining waste existing between the workpiece 2 and the wire electrode 3 from the histogram of the discharge current peak value, and the histogram of this discharge current peak value. The distribution value for the most frequent value is obtained from the distribution state of, and this dispersion value is compared with preset evaluation data (evaluation data that is already held), and each NPN type of the power supply circuit 4 is based on this comparison result. It has a function of evaluating the on timing of the transistors Q ₁ , Q ₂ , ... Qn, that is, the discharge timing.

Specifically, the power supply evaluation means 16-4 has a function of extracting a discharge current peak value that is not affected by machining waste existing between the workpiece 2 and the wire electrode 3 from the histogram of the discharge current peak value. .

That is, it is known that the histogram of the discharge current peak value has three dispersion forms from the first group to the third group as shown in FIG.

The discharge current peak value (normal discharge) belonging to the first group is in a state where the discharge gap is fully restored to insulation and the voltage is 100% charged, and is not greatly affected by the atmosphere of the discharge gap. The discharge is formed in the form closest to the set conditions.

The discharge current peak value (deionization discharge) belonging to the second group is
The discharge is started before reaching the 100% charge voltage, and the processing gaps and metal ions of the discharge generated immediately before are left in the discharge gap, and the insulation in the discharge gap is not restored.

The discharge current peak value (arc discharge) belonging to the third group is in a conductive state because the processing scraps and metal ions are buried in the discharge gap.

Therefore, the power supply evaluation means 16-4 extracts the discharge current peak value which is not affected by the machining waste, that is, the discharge current peak value of the first group from the discharge current peak values of the first group to the third group. It has a function.

Further, the power supply evaluation means 16-4 obtains the variance value σ for the most frequent value from the discharge current peak value (normal discharge) belonging to the first group, and compares this variance value σ with preset evaluation data. , Each NPN of the power supply circuit 4 based on this comparison result
Has a function of evaluating the on-timing of the type transistors Q ₁ , Q ₂ , ... Qn, that is, the discharge timing.

Here, the variance value σ is Represented by Note that N is the number, nk is the frequency, xk is a variable, and M is the most frequent frequency in the histogram.

Therefore, the power supply evaluation means 16-4 has the dispersion value σ (dispersion of discharge) and each NPN transistor Q of the power supply circuit 4.
₁ , Q ₂ , ... Qn are used as parameters for determining the on-timing of the on-timing, and a function of performing evaluation by comparing this dispersion value σ and data preset as evaluation data is provided.

Next, the operation of the apparatus configured as described above will be described.

A DC voltage is applied between the work piece 2 and the wire electrode 3 from a DC power source 5, and in this state the work piece 2 and the wire electrode 3 are applied.
When the gap amount between and becomes a predetermined amount, pulse discharge is generated between the workpiece 2 and the wire electrode 3. The workpiece 2 is processed by this pulse discharge energy.

In this state, the discharge current detector 7 detects the discharge current flowing from the workpiece 2 to the wire electrode 3 and outputs the discharge current detection signal, and the discharge voltage detector 7 connects the workpiece 2 and the wire electrode 3 to each other. The discharge voltage between the two is detected, and the discharge voltage detection signal is output. The discharge current detection signal and the discharge voltage detection signal are 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, respectively. At this time,
The A / D converters 13 and 14 simultaneously digitally convert the discharge current detection signal and the discharge voltage detection signal into 8-bit signals, for example, every xns in each signal sampling period at regular intervals ΔH. As a result, data of, for example, 1024 to 65536B is acquired in one signal sampling period. In this way, the digital discharge current detection signal and digital discharge voltage signal captured during one signal sampling period are each A / D
The data is temporarily stored in the memories in the converters 13 and 14, and is transferred to the RAM 18 by the CPU 16 and stored after the elapse of each signal sampling period.

In this way, for example, when the signal sampling period of 10 times is completed, the discharge data creating means 16-2 of the CPU 16 obtains the waveforms of the discharge voltage and the discharge current from the digital discharge current detection signal and the digital discharge voltage signal, respectively. Generating signals "1", "2" ... "N" are added in the order of discharge occurrence from the waveform. From these waveforms, the CPU 16 starts discharge a1, a2 ... An, discharge end b1, B2 ... Bn, discharge voltage c1, C2 ... Cn, discharge current peak value d1, d2 ... dn, current pulse width e1 from these waveforms. , e2 ... en, discharge energy f1, f2 ... fn, pulse interval g
The discharge data D consisting of parameters such as 1, g2 ... Gn are obtained and tabulated and stored in the RAM 18. Note that the discharge energies f1, f2 ... fn are the discharge voltage c1, c2 ... cn and the discharge current peak value.
It is calculated by multiplying d1, 2d ... dn respectively.

Next, the histogram creating means 16-3 takes out the respective discharge current peak values d1, d2 ... dn from the discharge data D and creates a histogram for the discharge current peak values, and further from this histogram the workpiece 2 and the wire electrode 3 Excludes the discharge current value that is affected by machining scraps existing between them. By the way, when a histogram is created for the peak value of the discharge current, this histogram has the following distributions. That is, in the histogram shown in FIG. 4, the discharge current peak values are all the same, and
The on timings of the N-type transistors Q ₁ , Q ₂ ... Qn match,
It shows that the maximum discharge energy is supplied.
Therefore, when the power supply evaluation means 16-4 receives the histogram shown in the figure, the power supply evaluation means 16-4 determines that the ON timings of the NPN transistors Q ₁ , Q _2, ... evaluate. The evaluation result is sent to the display drive unit 20 and the printer drive unit 21, and is displayed and printed out.

Next, when the histogram shows a normal distribution as shown in FIG. 5 and the variance value σ is large, the power supply evaluation means 16-4
The dispersion value σ and the evaluation data already held are compared and evaluated, and it is evaluated that the ON timings of the NPN transistors Q ₁ , Q _2, ...

Further, the histogram shown in FIG. 6 shows the distribution before excluding the discharge current value which is affected by the machining waste. That is, one distribution P ₁ is the discharge current belonging to the first group, and the other distribution P ₂ is the discharge current belonging to the second group and the third group.

Therefore, the power supply evaluation means 16-4 divides the histogram into two by the line S passing through the inflection points of the curve f connecting the highest values of the histogram to classify the first group and the second and third groups. It is judged that one of the distributions P ₁ indicates the discharge current in a state where the machining waste is removed by the flow of the machining fluid between the workpiece 2 and the wire electrode 3 and the state is sufficiently cleaned. , The other normal distribution P ₂ is judged to indicate the discharge current when the influence of the machining waste is given. Next, the histogram creating means 16
-3 is a histogram of only the discharge current peak value that is not affected by the machining waste shown in FIG. 7 except for the distribution P ₂ . Then, the power supply evaluation means 16-4 judges that this histogram shows a normal distribution and its variance value is small, and the power supply circuit 4
Although the NPN transistors Q ₁ , Q ₂ ... Qn have some variations in the on-timing, they are evaluated as being of a higher rank, for example, without affecting the electrical discharge machining.

Next, when the histogram has a very large variance value σ as shown in FIG. 8, the power source evaluation means 16-4 determines that the variance value σ is
It is determined that the variance value σ is very large by comparing the evaluation data that is already stored with the existing evaluation data, and the on-timing of each NPN transistor Q ₁ , Q ₂ , Qn is greatly shifted, and sufficient discharge energy is supplied. Evaluate it as impossible to do.

As described above, in the above-described embodiment, the histogram for the discharge current peak value is created, and the power supply timing of the power supply circuit 4 is evaluated based on the distribution state of the discharge current peak value in this histogram. It is possible to evaluate whether the ON timings of the NPN transistors Q ₁ , Q ₂ , and Qn in are coincident with each other. Therefore, based on this evaluation result, the power supply circuit 4 is set to the NPN type transistors Q ₁ , Q ₂ ... Qn.
With the same on-timing of each other and good performance to supply maximum discharge energy, or each transistor
It is impossible to supply high discharge energy due to variations in the ON timing of Q ₁ , Q ₂ ... Qn, and it can be evaluated as having poor performance. Since this evaluation is obtained from the histogram of the discharge current that is not affected by machining waste, an accurate evaluation result can be obtained. From the above, the power supply circuit 4 used for electric discharge machining can be evaluated by the user, and a power supply circuit with good performance can be selected to improve the accuracy and efficiency of electric discharge machining.

The present invention is not limited to the above embodiment, and may be modified without departing from the spirit of the invention. For example, although the histogram is created from the discharge current peak value in the above-described embodiment, the histogram may be created using the average value of the discharge current. In addition to wire electric discharge machining equipment, die-sinking electric discharge machining, electrolytic machining, and by changing the sampling range of voltage signals and current signals, welding machines, laser applied equipment, lighting equipment, sputtering equipment, plasma machining of PVD and CVD. It can also be applied to discharge application equipment such as devices. Among them, the sputtering apparatus can adjust the flow rate of the discharge medium by detecting the discharge state. Further, the CRT display 22 may display a part or all of the discharge data D, and the presence or absence of rigging by using figures or numerical values.

[Effects of the Invention] As described in detail above, according to the present invention, each switching element of a power supply circuit that sequentially operates a plurality of switching elements connected in parallel to supply power between a workpiece and a discharge electrode. It is possible to provide a power supply evaluation device in electric discharge machining that can evaluate the operation timing of the.

[Brief description of drawings]

1 to 8 are views for explaining an embodiment of a power supply evaluation apparatus in electric discharge machining according to the present invention. FIG. 1 is a configuration diagram, FIG. 2 is a functional block diagram, and FIG. 8 to 8 are diagrams for explaining the operation of power source evaluation. 1 ... Machining tank, 2 ... Workpiece, 3 ... Wire electrode, 4
...... Power supply circuit, 5 ...... DC power supply, 6 ...... Base current supply circuit, 7 ...... Discharge current detector, 8 ...... Discharge voltage detector,
10 ... Power supply evaluation device main unit, 11, 12 ... Attenuator, 13,
14 …… A / D converter, 15 …… bus, 16 …… CPU, 16-1 ……
Signal collecting means, 16-2 ... Discharge data creating means, 16-3
...... Histogram creation means, 16-4 …… Power supply evaluation means,
17 …… Timing controller, 18 …… RAM, 19 …… RO
M, 20 …… Display drive, 21 …… Printer drive, 22 …… C
RT display, 23 ... Printer.

Claims (1)

[Claims] 1. A power supply evaluation in electric discharge machining for evaluating the operation timing of each switching element of a power supply circuit for supplying electric power between a workpiece and a discharge electrode by sequentially operating a plurality of switching elements connected in parallel. In the device, a discharge current detector that detects a discharge current flowing between the workpiece and the discharge electrode, and a peak value of the discharge current is extracted by receiving a current detection signal from the discharge current detector. Histogram creating means for creating a histogram for the discharge current peak value, and a variance value for the mode value is obtained from the distribution state of the histogram of the discharge current peak value created by the histogram creating means, and this variance value is preset. The evaluation data are compared with each other, and each switching element in the power supply circuit is based on the comparison result. Power evaluation device in electrical discharge machining, characterized by comprising a power supply evaluation means for evaluating for operation timings, the.