JPH08290329A - Machining state monitor for electric discharge machine - Google Patents

Abstract

PURPOSE: To accurately evaluate a machining state on the basis of objective data by providing a display means for displaying the integrated time, measured by a voltage distribution measuring means, in correspondence with each voltage range. CONSTITUTION: Gap average voltage outputted from a low-pass filter 1 serving as a gap average voltage detecting means is inputted to a voltage distribution measuring means 2. Processing on the comparison between several preset voltage ranges and the gap average voltage outputted from the low-pass filter, and processing for integrating and measuring the detected time of the gap average voltage every voltage range according to the compared result are executed by the voltage distribution measuring means 2 over the specified time length. A reading means 3 reads the measured data of every voltage range and graphically displays the result by a bar graph or the like on a display means 4. The reading means 3 and the display means 4 can be independently formed, or these functions can be performed by a control device 100 and its CRT/MDI.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a machining status monitor for an electric discharge machine.

[0002]

2. Description of the Related Art The stability of the average voltage of the gap between an electrode and a work piece affects whether the machining accuracy of electric discharge machining is good or bad. It is generally well known from the fact that the gap average voltage changes when the required time up to and the gap average voltage becomes zero when the electrode and the workpiece are short-circuited.

By utilizing such a phenomenon, the gap average voltage or its current is displayed on a pointer type analog meter to judge the occurrence of electric discharge, that is, the machining status of the electric discharge machine. A processing status monitor device is known.

[0004]

In the monitoring of the discharge occurrence state using a pointer type analog meter, since the pointer fluctuates according to the gap average voltage or the average discharge current, the discharge stability is judged from the fluctuation of the pointer. However, it is difficult to make the judgment because the discharge stability is judged by the changing guide. The operator roughly memorizes the repeated movement of the pointer for one cycle when the machining is normally performed, and thereafter compares the movement of the pointer at that time with that of the past, relying on his own memory. Although it is determined whether or not there is an abnormality, a correct result cannot always be obtained because the determination becomes subjective, and appropriate experience is required to make a reasonable determination. Moreover, since much of the judgment depends on the subjectivity, it is very difficult to determine the cause of the abnormality.

Therefore, a main object of the present invention is to solve the above-mentioned drawbacks of the prior art, and, first, to provide a machining status monitor device for an electric discharge machine capable of accurately evaluating the machining status based on objective data. To do.

Further, it is possible to visually display objective data to facilitate the evaluation of the machining status, and to easily grasp the fluctuation of the machining status by showing the data change in time series. It is also an object of the present invention to allow objective data extraction criteria to be arbitrarily changed and set so that the machining status can be monitored by coping with various electrical discharge machining conditions.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a gap average voltage detecting means for detecting and outputting a gap average voltage between an electrode and a workpiece, some preset voltage ranges and the gap average voltage detection. Voltage distribution measuring means for comparing the gap average voltage output from the means, and integrating and measuring the time during which the gap average voltage is included in each voltage range over a preset time length, and the voltage distribution measurement With a configuration characterized by including display means for displaying the integrated time measured by the means in correspondence with each voltage range, it is possible to accurately evaluate the machining situation by objective data (claim) 1).

Further, by adopting the display means for displaying the integrated time measured by the voltage distribution measuring means in a graph corresponding to each voltage range, the machining situation can be easily evaluated (claim 2). .

Further, by adopting the voltage distribution measuring means and the display means which are repeatedly operated for the time length, it is possible to easily grasp the variation of the machining situation (claim 3).

Further, as a substantial means for realizing the function of the voltage distribution measuring means, a clock pulse generator,
The gap average voltage output by the gap average voltage detection means is compared between whether or not it is included between the upper limit voltage and the lower limit voltage of the set voltage range, and only when it is included, the voltage range is supported. A voltage comparator for outputting a signal to a frequency counter provided for each voltage range, and a frequency counter for each voltage range for counting clock pulses while a signal is input from the voltage comparator. The configuration of the distribution measuring means (claim 4) and whether or not the gap average voltage output by the gap average voltage detecting means is included between the upper limit voltage and the lower limit voltage of the set voltage range are compared. A voltage comparator that outputs a signal to the voltage averaging means provided corresponding to the voltage range only when included, and a voltage averaging provided corresponding to each voltage range Proposed a stage, a structure (claim 5) of the voltage distribution measuring means comprising an A / D converter for each voltage range for digitizing the output from each voltage averaging means.

For the configuration using the voltage comparator as the comparison means in the voltage distribution measuring means, a register for storing the upper limit voltage value and the lower limit voltage value of each voltage range and the value of each register are converted into an analog signal. By providing a D / A converter that outputs to the corresponding voltage comparator and changing the value set in the register to arbitrarily change the upper limit voltage and lower limit voltage of each voltage range, various processing conditions are dealt with. It is possible to accurately evaluate the machining situation (claim 6).

Further, as means for realizing the function of the voltage distribution measuring means, further, a sample hold circuit for sample-holding and outputting the gap average voltage output by the gap average voltage detecting means every predetermined period, An A / D conversion circuit for converting the output of the sample hold circuit into a digital signal, a code conversion circuit for outputting the output from the A / D conversion circuit by dividing it into several preset voltage ranges, and the code. If there is an output signal in the corresponding voltage range from the conversion circuit, a voltage distribution measuring means composed of a frequency counter for each voltage range that counts up in synchronization with the execution of the sample hold (claim 7), and a gap. A sample hold for sampling and holding the gap average voltage output by the average voltage detecting means at predetermined intervals. A road, and A / D converter for digitally converting an output from said sample-and-hold circuit, A /
Memory means for storing an output value from the D converter at an address which is sequentially updated in synchronization with the execution of the sample and hold over a preset time length; and each of the values stored in the memory means. A configuration (claim 8) of voltage distribution measuring means including a statistical processing means for counting the number of values included in the voltage range for each of the voltage ranges is proposed.

[0013]

The gap average voltage detecting means sequentially detects the gap average voltage between the electrode and the workpiece, and the voltage distribution measuring means compares some preset voltage ranges with the detected gap average voltage. The time during which the gap average voltage is included in each voltage range is integrated and measured for each voltage range within a predetermined time length range. The display means displays the integrated time for each voltage range, that is, the relative proportion of the time during which the gap average voltage belongs to each voltage range, in association with each voltage range, and informs the operator. So, for example,
If the time ratio of the gap average voltage included in the voltage range corresponding to the ideal gap average voltage under that processing condition is large, it can be determined that normal processing is being performed, and the gap average It can be seen that when the time ratio occupied by the voltage varies in various voltage ranges, the discharge is unstable and there is no constant repeatability. If the time ratio of the gap average voltage included in the voltage range close to zero is large, it can be determined that a short circuit or the like has occurred between the electrode and the workpiece (claim 1).

When the voltage distribution measuring means is composed of a clock pulse generator, a voltage comparator and a frequency counter, the clock pulse generator generates a clock pulse at every predetermined cycle. In the voltage comparator for each voltage range, the gap average voltage output by the gap average voltage detection means is included between the upper limit voltage and the lower limit voltage of the voltage range set for the voltage comparator. Compare whether or not. Then, only when the gap average voltage is included in the set voltage range, the voltage comparator outputs a signal to the frequency counter provided corresponding to the voltage range. The frequency counter for each voltage range counts the clock pulses only while the signal is input from the voltage comparator, and this value is used for the entire gap average voltage detection time (predetermined time length) in that voltage range. It is output to the display means and displayed as a time ratio (claim 4).

A voltage comparator, voltage averaging means, A /
In the case of the voltage distribution measuring means constituted by the D converter, the voltage comparator for each voltage range is composed of the upper limit voltage and the lower limit voltage of the voltage range in which the gap average voltage output by the gap average voltage detecting means is set. Whether the gap average voltage is included or not is compared, and only when the gap average voltage is included in the set voltage range, a signal is output to the frequency counter provided corresponding to the voltage range. That is, this signal is ON only while the gap average voltage is included in the set voltage range, and is OFF in other cases. Since the voltage averaging means provided corresponding to each voltage range averages this signal, as a result, its output value is a ratio of the ON time of the signal to a predetermined time length,
In short, the detection time of the gap average voltage in that voltage range is proportional to the time ratio to the whole. The A / D converter for each voltage range digitizes the output from the voltage averaging means and outputs it to the display means for display (claim 5).

Further, in the voltage distribution measuring means composed of the sample hold circuit, the A / D conversion circuit, the code conversion circuit, and the frequency counter, the sample hold circuit has the gap average for each predetermined period shorter than the predetermined time length. The output of the voltage detecting means is sample-held and output to the A / D conversion circuit for conversion into a digital signal. The code conversion circuit divides the output from the A / D conversion circuit into some preset voltage ranges and outputs the divided voltage ranges. The frequency counter for each voltage range outputs the output signal of the corresponding voltage range from the code conversion circuit. Only when there is, the coefficient value is incremented in synchronization with the execution of the sample hold. The value of the frequency counter for each voltage range is the time ratio of the detection time of the gap average voltage in that voltage range to the whole. The frequency counter outputs and displays the value on the display means (claim 7).

Further, in the voltage distribution measuring means composed of the sample and hold circuit, the A / D converter, the memory means and the statistical processing means, the sample and hold circuit is provided at every predetermined cycle which is sufficiently shorter than the predetermined time length. The output of the gap average voltage detecting means is sample-held and output to the A / D conversion circuit for conversion into a digital signal. The memory means stores the output value from the A / D converter at the address updated in synchronization with the execution of the sample hold for the preset time length. The statistical processing means counts, for each voltage range, the number of values included in each voltage range by referring to the memory means when the preset time length has elapsed, and the value of the voltage range The detection time of the gap average voltage is output to the display means and displayed as a time ratio to the whole (claim 8).

Since the display means displays the integrated time measured by the voltage distribution measuring means in a graph corresponding to each voltage range, the operator can easily grasp the time ratio occupied by the gap average voltage in each voltage range. Therefore, it is possible to easily evaluate the occurrence status of the discharge, that is, the processing status (claim 2).

Further, since the voltage distribution measuring means and the display means are repeatedly operated for the above-mentioned time length, the display means has a time ratio occupied by the gap average voltage of each voltage range immediately before that time. Will be sequentially updated and displayed. Therefore, the operator can know whether the change in the time ratio occupied by the gap average voltage in each voltage range has a tendency to increase in a time series or a tendency to decrease, and the like. The change in the situation can be easily grasped (Claim 3).

In the voltage distribution measuring means, a voltage comparator is used as means for comparing the voltage range and the gap average voltage (configurations of claims 4 and 5).
Various processing is performed in a configuration in which a register that stores the upper limit voltage value and the lower limit voltage value of each voltage range and a D / A converter that converts the value of each register into an analog signal and outputs the analog signal to the corresponding voltage comparator are provided. By changing the value set in the register according to the condition and arbitrarily changing the upper limit voltage and lower limit voltage of each voltage range, various machining conditions can be dealt with and the machining status of the electrical discharge machine can be accurately evaluated. It is possible (claim 6).

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram schematically showing the configuration of a die-sinking electric discharge machine to which a machining status monitor device according to an embodiment of the present invention is attached. In FIG. 1, SC is a switching element that is ON / OFF controlled by a control device 100 of the die-sinking electric discharge machine, R1 is a current limiting resistor, and these are formed on the electrode 101 and the workpiece 102 of the die-sinking electric discharge machine. A machining voltage is applied from the machining DC power source Vc via the element. The low-pass filter 1 is for obtaining a gap average voltage by removing a high frequency fluctuation from the gap voltage divided by the resistors R2 and R3, and constitutes a substantial gap average voltage detecting means.

Although not particularly shown in FIG. 1,
A discharge detector for detecting the occurrence of discharge by detecting a change in the gap voltage divided by the resistors R2 and R3 is provided in the same manner as the conventional one, and the switching element SC is turned on.
The / OFF control is performed by the discharge detector and the control device 100 in the same manner as in the conventional case.

That is, taking one discharge cycle as an example, first, the control device 100 causes the switching element SC to operate.
Is closed and a processing voltage is applied to the electrode 101 and the workpiece 102, and when this voltage application causes dielectric breakdown, the electrode 1
No. 01 and the workpiece 102 generate an electric discharge to perform destructive machining. Simultaneously with the occurrence of discharge, the gap voltage divided by the resistors R2 and R3 also drops, and the discharge detector detects this and outputs a discharge detection signal to the control device 100. The control device 100 receiving the discharge detection signal from the discharge detector,
After the closed state of the switching element SC is further held for a predetermined time to perform machining by electric discharge, the switching element SC is opened to stop the application of the machining voltage for a predetermined time in order to restore insulation between the electrodes. This is the operation of one discharge cycle. Hereinafter, the electric discharge cycle similar to the above is repeatedly executed during the continuation of the machining, and this point is exactly the same as the control of the conventional die-sinking electric discharge machine.

Therefore, as long as normal electric discharge machining is performed and the time required from the start of voltage application to the occurrence of dielectric breakdown is constant, the relationship between the change in gap voltage and the elapsed time is shown in FIG.
As shown in (a). Further, according to this control method, even when the time required from the start of voltage application to the occurrence of dielectric breakdown changes due to fluctuations in processing conditions, etc., as shown in FIG. O
The FF time and the discharge current flow time are constant.

Further, in this embodiment, the gap average voltage output from the low-pass filter 1 as the gap average voltage detecting means is input to the voltage distribution measuring means 2,
Several preset voltage ranges and low pass filter 1
The process for comparison with the gap average voltage output from, and the process for integrating and measuring the detection time of the gap average voltage for each voltage range according to the comparison result,
The voltage distribution measuring means 2 carries out the operation for a predetermined length of time. Then, the reading means 3 reads the measurement data for each voltage range, and the result is displayed on the display means 4 as a bar graph or the like. The reading means 3 and the display means 4 may be configured separately, and the control device 100 may be used.
Alternatively, the CRT / MDI (manual data input device with display device) may be used.

FIG. 2 is a block diagram showing an example of the configuration of the voltage distribution measuring means 2. In this embodiment, the voltage range to be compared with the gap average voltage is set over N stages, and the voltage distribution measuring means 2 is provided for each stage of the voltage range to be compared with the gap average voltage. The comparison level generating means 5 for setting the upper limit voltage 1A to NA and the lower limit voltage 1B to NB of each stage, the clock pulse generator 6, the voltage comparators 7-1 to 7-N of each stage, and each stage. It is composed of frequency counters 8-1 to 8-N.

The comparison level generating means 5, for example, as shown in FIG. 3, has an upper limit voltage value storage register 11-iA for setting the upper limit voltage value iA of the voltage range of the i-th stage and D corresponding thereto. A / A converter 12-iA, a lower limit voltage value storage register 11-iB for setting the lower limit voltage value iB of the voltage range of the i-th stage, and a D / A converter 12-iB corresponding thereto. , These are i = 1 to i =
By providing over the range of N, the voltage range of N stages is dealt with. In such a configuration, setting and changing of the upper limit voltage values 1A to NA and the lower limit voltage values 1B to NB are arbitrary, and the upper limit voltage value and the lower limit voltage value of each voltage range are rough machining, finishing machining, etc. It should be decided according to the discharge conditions of.

The most general method for setting the voltage range is to set the voltage ranges so that they do not overlap and are in close contact with each other, as shown in FIG.
In this case, the upper limit voltage value iA of the voltage range of the i-th stage and the i + th
Since the lower limit voltage value i + 1B of one stage has the same value in the range of i = 1 to i = N−1, the total number of registers and the total number of D / A converters required in FIG. 3 are 2N ( It is possible to save N + 1 pieces from the example of FIG. For example, in FIG. 3, the register 11-iB and the D / A converter 12-iB belonging to the series whose code end is B are i = 2.
To i = N, i = 1 to i = N
In the range of −1, the register 11-iA is set to the value of the reference voltage value Vi which is the upper limit voltage value of the voltage range of the i-th stage and is also the lower limit voltage value of the voltage range of the i + 1-th stage. The output from the D / A converter 12-iA for D / A converting the value is used as the upper limit voltage of the voltage range for the voltage comparator 7-i, and for the voltage comparator 7- (i + 1). May be input as the lower limit voltage of the voltage range. Of course, the upper limit voltage setting for the Nth stage (final stage) voltage comparator 7-N and the lower limit voltage setting for the first stage (first stage) voltage comparator 7-1 are individually performed. Since a register and a D / A converter are required, a set of a register 11-NA and a D / A converter 12-NA and a register 11-1B and a D / A are required for these.
It is necessary to fill a set of converters 12-1B (the ones not removed). In the first stage, the lower limit voltage may be set below the upper limit voltage and the lower limit voltage may not be set. In this case, the register 11-1B and the D / A conversion circuit 12-1B are not necessary. In addition, the voltage comparator 7-1 of the first stage has the upper limit voltage 1 to which the gap average voltage is input.
Output is output when A or less.

As shown in FIG. 2, the gap average voltage from the low-pass filter 1 is input in parallel to all the voltage comparators 7-i of i = 1 to i = N. Then, each voltage comparator 7-i determines this voltage comparator only when it determines that the current value of the gap average voltage is between the upper limit voltage iA and the lower limit voltage iB set for each of them. For the frequency counter 8-i corresponding to 7-i,
Count enable signal that enables count up operation
Output EN-i.

The output from the clock pulse generator 6 is logically ANDed with the count enable signal EN-i from the voltage comparator 7-i and input to each of the frequency counters 8-i. The count enable signal EN-i is input to each of the frequency counters 8-i, and the reading means 3
Only when the measurement signal TS from is active, the number of clock pulses from the clock pulse generator 6 is integrated.

When the measurement signal TS from the reading means 3 changes to the inactive state, the frequency counter 8-i.
When the count-up operation is stopped and the value of the integrated value at that time is held as it is in the frequency counter 8-i, and the measurement signal TS from the reading means 3 changes to the active state again, the value of the frequency counter 8-i. Is reset to zero and restart of the count-up operation of the counter 8-i is permitted. The measurement signal TS is output from the reading means 3, and is a rectangular wave that produces an inactive state (Lo level) at every predetermined cycle for convenience.
The reading means 3 reads the integrated value (described as voltage distribution measurement data in FIG. 2) of each frequency counter 8-i while the measurement signal TS is inactive, and the value of each integrated value is set in the voltage range. The display means 4 is caused to display a graph by using a display system such as a bar graph.

That is, the integrated value of the frequency counter 8-i displayed corresponding to each voltage range is the upper limit voltage iA in the cycle (predetermined time length) from the rise to the fall of the measurement signal TS. And the lower limit voltage iB is the total time during which the gap average voltage is detected.

Correspondence between the variation of the gap average voltage and the voltage range when the electric discharge machining is normally performed, and
A display example of a bar graph corresponding to this is shown in FIGS. 6 (a) and 6 (b). FIG. 6A shows the case where four voltage ranges of (1) to (4) are set in the ascending order of the gap average voltage. While the electric discharge machining is normally performed, other voltage ranges are set. The gap average voltage is detected in the voltage range (3) for a significantly longer time than
It is clear from the bar graph of FIG.

Of course, theoretically, it is possible to monitor the occurrence of discharge by displaying the time series data as shown in FIG. 6 (a) as it is, but the gap average from the low pass filter 1 is monitored. A high-speed microprocessor or the like is required to perform display processing for A / D converting the voltage output in real time to generate a diagram as shown in FIG. 6 (a). It is disadvantageous in that a high-level graphic display is required as the display means 4 for displaying the schematic diagram, and further that the operator needs some basic knowledge to analyze the diagram. Is.

On the other hand, as in the present embodiment, by the processing on the hardware, the detection time of the gap average voltage for each voltage range is integrated in a relatively long time period from the rise to the fall of the measurement signal TS. If the values are obtained and displayed in a bar graph form collectively, the bar graph display can be switched at each cycle of the measurement signal TS, and at that time, no arithmetic processing is required. The control unit of the reading means 3 does not need an excessive processing capacity, and the display device 4 itself can perform its function even if it is an LED display device having a simple structure for displaying a bar graph. Also,
Time-series elements are deleted from the data, and only the weight of the time ratio at which the gap average voltage is detected is directly displayed for each voltage range, so the operator can perform electrical discharge machining without any analysis work. The discharge occurrence state of the machine can be grasped intuitively, which is very convenient for the operator side.

FIG. 7 (a) is a diagram showing the correspondence relationship between the fluctuation of the gap average voltage and the voltage range when the discharge becomes unstable, and FIG. 7 (b) corresponds to FIG. 7 (a). It is a display example of a bar graph, and as is clear from FIG. 7B, the time ratio occupied by the voltage range (3) of the gap average voltage when the electric discharge machining is normally performed is decreased, and before and after that,
In short, it can be seen that the time ratio occupied by the gap average voltage in the voltage range (2) slightly lower than the voltage range (3) and in the voltage range (4) slightly higher than the voltage range (3) increases. Further, FIG. 8A is a diagram showing a correspondence relationship between the variation of the gap average voltage and the voltage range when a short circuit occurs between the electrode 101 and the workpiece 102, and FIG. Figure 8
8 is a display example of a bar graph corresponding to FIG.
As is apparent from (b), the time ratio occupied by the voltage range (3) of the gap average voltage when the electric discharge machining is normally performed is reduced, and the voltage range (2) lower than the voltage range (3). , (1), the time ratio occupied by the gap average voltage is large, and in particular, the time ratio occupied by the lowest voltage range (1) is significantly increased. As described above, when both the time ratios occupied by the voltage ranges located before and after the voltage range of the gap average voltage in the case where the electric discharge machining is normally performed are both increased (the example in FIG. 7B), the discharge is not completed. In the case where only the time ratio occupied by the voltage range lower than the voltage range of the gap average voltage when the electric discharge machining is normally performed is increased (in FIG. 8B). In the example), it can be considered that a discharge abnormality due to a short circuit has occurred.

Further, the bar graph display is switched by the measurement signal T.
Since it is automatically executed repeatedly every S cycles, the operator can easily grasp the variation of the discharge occurrence situation, that is, the machining situation variation by watching the variation of the bar graph display of the display device 4. it can. For example, the time ratio occupied by the voltage range (3) gradually decreases from the display state as shown in FIG. 6B, and the time ratio occupied by the voltage ranges (2) and (4) before and after that gradually increases. If there is a tendency, it can be seen that the discharge is sporadically becoming unstable. In addition, FIG.
From the display state shown in (b), the time ratio occupied by the voltage range (3) gradually decreases, and only the time ratio occupied by the lower voltage ranges (2) and (1) gradually increases. If so, a short circuit actually occurs and the bar graph is shown in Fig. 8.
Even before the state shown in FIG.
It can be predicted that a short circuit may occur between the workpiece 1 and the processed portion 102.

FIG. 4 shows the frequency counter 8-1 shown in FIG.
~ 8-N, low-pass filters 9-1 to 9-N and A / D converters 10-1 to 10-N as voltage averaging means.
FIG. 9 is a block diagram showing an outline of a configuration of another embodiment in which the voltage distribution measuring means 2 is configured by using the. The structure of the comparison level generating means 5 and the voltage comparators 7-1 to 7-N is the same as that of the embodiment shown in FIG. 2, but the clock pulse generator 6 is unnecessary in this embodiment, and the low pass filter is used. The count enable signals EN-1 to EN-N of the voltage comparators 7-1 to 7-N are only input to 9-1 to 9-N.

The low pass filters 9-1 to 9-N have count enable signals EN from the voltage comparators 7-1 to 7-N.
-1 to EN-N are averaged and A / D converters 10-1 to 10-N
Is output to the reading means 3 via the display means 4 and the bar graph is displayed on the display means 4 in the same manner as in the above embodiment. If the ON time of the count enable signal EN-i from the voltage comparator 7-i corresponding to a specific voltage range is long, the value of the voltage of the count enable signal EN-i averaged by the low-pass filter 9-i Therefore, the bar graph display result is long in the voltage range in which the gap average voltage is detected between the upper limit voltage iA and the lower limit voltage iB for a long time, as in the above embodiment. If the time is short, the bar graph will be displayed short.

9, instead of the comparison level generating means 5, the voltage comparators 7-1 to 7-N and the clock pulse generating circuit 6 shown in FIG. 2, a sample hold circuit 13, an A / D conversion circuit 14, 9 is a block diagram showing the outline of the configuration of yet another embodiment in which the voltage distribution measuring means 2 is configured by using the code conversion circuit 15 and the timing pulse generation circuit 16. FIG.

The sample hold circuit 13 receives the timing pulse T1 from the timing pulse generation circuit 16, samples and holds the gap average voltage from the low pass filter 1, and outputs its analog value to the A / D conversion circuit 14. Naturally, the cycle of the timing pulse T1 is sufficiently shorter than the cycle of the measurement signal TS having a predetermined time length.
During the S cycle, the sample hold is executed a plurality of times.

The A / D conversion circuit 14 is a parallel comparison type A / D conversion circuit.
At that time, the signals input from the sample hold circuit 13 are simultaneously compared and discriminated, and the value of each bit of the gray code corresponding to the boundary to which the input value belongs is converted into the code conversion circuit 1.
5 is output in parallel. The code conversion circuit 15 determines which voltage range the gray code is included in, among several preset voltage ranges, and selects one of EN-1 to EN-N according to the corresponding voltage range. One count enable signal EN-i is sent to the corresponding frequency counter 8-i.
Output to. Since the step size of the quantization step of the A / D conversion circuit 14 is specified by the standard of the A / D conversion circuit 14 as a product, unlike the configuration example of FIG.
Since it is impossible to change the setting of the voltage range by changing the setting of the input of the comparison reference value to each comparison circuit included in the conversion circuit 14, it is necessary to change the setting of the voltage range to the code conversion circuit 15. To do it. Therefore, the code conversion circuit 15 substantially also functions as the comparison level generating means 5 as shown in FIG.

Count enable signals EN-1 to EN-N from the code conversion circuit 15 are input to the frequency counters 8-1 to 8-N by ANDing with the timing pulse T2 from the timing pulse generation circuit 16. And each element 13, 1
Timing pulse T corresponding to the required operation time of 4, 15
Timing pulse T2 output slightly later than 1
The frequency counter 8 in which the count enable signal is ON corresponding to the gap average voltage sampled and held at that time only when the measurement signal TS from the reading means 3 is active in response to the input of -I
Only count up.

Then, the measurement signal TS from the reading means 3
Is changed to the inactive state, the frequency counter 8-
The count-up operation of 1 to 8-N is stopped, and the value of the integrated value at that time is the same as that of the frequency counters 8-1 to 8-
When held at N and the measurement signal TS from the reading means 3 changes to the active state again, the frequency counters 8-1 to 8-1.
The value of 8-N is reset to zero and the counter 8-
The restart of the count-up operation of 1 to 8-N is allowed.
The reading means 3 reads the integrated value of each of the frequency counters 8-1 to 8-N while the measurement signal TS is inactive, associates the value of each integrated value with the voltage range, and displays the bar graph or the like. A graph is displayed on the display means 4 using the display method. This point is the same as the embodiment shown in FIG. In the present embodiment, since the existing A / D conversion circuit 14 is used to perform the processing on the hardware,
The cost of the device can be reduced more easily than in the case where a special configuration as shown in FIG. 2 is applied.

FIG. 10 is a sample hold instead of the comparison level generating means 5, the voltage comparators 7-1 to 7-N, the clock pulse generating circuit 6, and the frequency counters 8-1 to 8-N shown in FIG. Circuit 13, A / D converter 20, memory 17,
9 is a block diagram showing the outline of the configuration of yet another embodiment in which the voltage distribution measuring means 2 is configured by using the statistical processing means 18, the timing pulse generating circuit 16, and the address generating circuit 19. FIG.

The average gap voltage output from the low pass filter 1 is sampled and held by the sample and hold circuit 13 by the timing pulse T1 from the timing pulse generation circuit 16, and the held voltage is converted into a digital signal by the A / D conversion circuit 14. And outputs it to the memory 17. The memory 17 outputs the timing pulse T1 output from the timing pulse generation circuit 16 for a predetermined time length TS.
In the address generator 19 that has a storage address equal to twice the number of times (= the number of timing pulses T2) and receives the timing pulse T2 output slightly after the timing pulse T1 to update the designated address. Upon receiving the designated address command, the value of the gap average voltage at each time output from the A / D conversion circuit 14 is stored in time series. For example, if the value of TS cycle / T1 cycle is n, the memory 17 as a whole has 2n (address value 1 to 2n) storage addresses.
The address generator 19 is reset after designating the final address, and again designates the address from the first address.

Further, when the value of the address becomes n + 1 and when it becomes 1, the address generator 19 outputs the statistical execution commands S1 and S2 to the statistical processing means 18.

Statistical processing means 1 which has received the statistical execution command S1
8 searches for data at addresses 1 to n in the memory 17,
The number of data contained in each of several preset voltage ranges is cumulatively counted for each voltage range, and the value of each integrated value is output to the reading means 3 in association with each voltage range. The display means 4 is caused to display a graph using a display system such as a bar graph. When the statistics execution command S2 is received, the same processing as described above is performed on the data at the addresses n + 1 to 2n in the memory 17, and the graph display is executed. While the statistical processing is being performed, the write operation of the gap average voltage at that time is performed in the memory 17 according to the address designation from the address generator 19, but the statistical processing means 18 While the data of addresses 1 to n are being processed, writing to addresses n + 1 and onward is performed, and while the statistical processing means 18 is processing the data of addresses n + 1 to 2n, writing to addresses n and below is performed. As it is done, the data being processed is not compromised. As a result, the display result displayed on the display means 4 is delayed by one cycle with reference to the predetermined time length TS.

[0049]

According to the machining status monitor of the electric discharge machine of the present invention, several voltage ranges are determined in advance, and the time during which the gap average voltage is included in each voltage range is set for a preset time length. Since the integrated measurement is displayed for each voltage range and displayed, it is different from the conventional monitoring device that monitors the change in the deflection of the pointer-type voltmeter or ammeter to judge the discharge occurrence status. It is possible to directly and objectively know the degree of gap average voltage variation without having to analyze the subject or make a subjective judgment. The occurrence of an abnormality such as a short circuit between the workpiece and the workpiece can be extremely easily detected.

Further, since the measured integrated time is displayed in a graph corresponding to each voltage range, it is very easy to grasp the displayed data.

Further, since the graph display showing the degree of variation in the gap average voltage is rewritten repeatedly at a predetermined cycle reflecting the discharge state at that time, the tendency of the graph display changes, for example, the ideal gap average. The gap average voltage starts to be detected before and after the voltage is sandwiched, or only the gap average voltage lower than the ideal gap average voltage starts to be detected for a long time, which adversely affects the machining. It is also possible to predict the occurrence of an abnormality at a stage before the unstable discharge phenomenon that actually occurs or the short circuit between the electrode and the workpiece actually occurs.

In the voltage distribution measuring means, the means for determining the upper limit value and the lower limit value of the voltage range is formed by a register, a D / A converter and a voltage comparator having a specific configuration so that the voltage range can be set arbitrarily. Therefore, reliable abnormality detection can be performed by coping with differences in various processing conditions such as high and low discharge voltage, and a main part of the voltage distribution measuring means such as a commercially available parallel comparison type. If the A / D conversion circuit is used, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a functional block diagram schematically showing a configuration of a die-sinking electric discharge machine to which a machining status monitor device according to an embodiment of the present invention is attached.

FIG. 2 is a block diagram showing a configuration example of voltage distribution measuring means of the same embodiment.

FIG. 3 is a block diagram showing a configuration example of a comparison level generating means in the voltage distribution measuring means of the embodiment.

FIG. 4 is a block diagram showing a configuration example of voltage distribution measuring means of another embodiment.

FIG. 5 is a diagram exemplifying electric discharge control in die-sinking electric discharge machining.

FIG. 6 is a diagram showing a correspondence relationship between a variation in the gap average voltage and a voltage range when electric discharge machining is normally performed, and a display example of a bar graph corresponding to the correspondence relationship.

FIG. 7 is a diagram showing a correspondence relationship between a change in the gap average voltage and a voltage range when the discharge becomes unstable, and a display example of a bar graph corresponding to the correspondence relationship.

FIG. 8 is a diagram showing a correspondence relationship between a change in gap average voltage and a voltage range when a short circuit occurs between an electrode and a workpiece, and a display example of a bar graph corresponding to the correspondence relationship.

FIG. 9 is a block diagram showing a configuration example of a voltage distribution measuring means of still another embodiment.

FIG. 10 is a block diagram showing a configuration example of a voltage distribution measuring unit according to still another embodiment.

[Explanation of symbols]

 SC switching element R1 current limiting resistance R2 resistance R3 resistance Vc machining DC power supply EN-1 to EN-N count enable signal TS measurement signal T1 timing pulse T2 timing pulse 1 low pass filter (gap average voltage detection means) 2 voltage distribution measurement means 3 reading means 4 display means 5 comparison level generating means 6 clock pulse generator 7-1 to 7-N voltage comparator 8-1 to 8-N frequency counter 9-1 to 9-N low-pass filter 10-1 to 10- NA / D converter 11-1A to 11-NA Upper limit voltage value storage register 11-1B to 11-NB Lower limit voltage value storage register 12-1A to 12-NA D / A converter 12-1B to 12-NB D / A converter 13 Sample and hold circuit 14 A / D conversion circuit 15 Sign conversion circuit 16 Timing pulse generation circuit 17 memory 18 statistical processing means 19 address generation circuit 20 A / D converter 100 controller 101 electrode 102 workpiece

Claims (8)

[Claims] 1. A gap average voltage detection means for detecting and outputting a gap average voltage between an electrode and a workpiece, some preset voltage ranges, and a gap average voltage output from the gap average voltage detection means. And a voltage distribution measuring means for integrating and measuring the time during which the gap average voltage is included in each voltage range for each voltage range over a preset time length, and the integration measured by the voltage distribution measuring means. A machining status monitoring device for an electric discharge machine, comprising: a display unit that displays time corresponding to each voltage range. 2. The machining status monitor device for an electric discharge machine according to claim 1, wherein the display means displays the integrated time measured by the voltage distribution measuring means in a graph corresponding to each voltage range. 3. The machining status monitor device for an electric discharge machine according to claim 1, wherein the voltage distribution measuring means and the display means are repeatedly operated for the time length. 4. The voltage distribution measuring means is included between a clock pulse generator and an upper limit voltage and a lower limit voltage of a voltage range in which the gap average voltage output by the gap average voltage detecting means is set. If there is a voltage comparator for each voltage range that outputs a signal to a frequency counter provided corresponding to the voltage range only when it is included, a signal from the voltage comparator is output. 4. A machining status monitor device for an electric discharge machine according to claim 1, wherein the machining status monitor device comprises a frequency counter for each voltage range that counts clock pulses while being input. 5. The voltage distribution measuring means compares whether or not the gap average voltage output by the gap average voltage detecting means is included between an upper limit voltage and a lower limit voltage of a set voltage range. A voltage comparator that outputs a signal to the voltage averaging means provided corresponding to the voltage range only when included, and a voltage averaging means provided corresponding to each voltage range, 4. The electric discharge machine according to claim 1, wherein the electric discharge machine comprises an A / D converter for each voltage range that digitizes the output from each voltage averaging means. Processing status monitor device. 6. A register for storing an upper limit voltage value and a lower limit voltage value of each voltage range, and a D / A converter for converting the value of each register into an analog signal and outputting the analog signal to a corresponding voltage comparator, The machining status monitoring device for an electric discharge machine according to claim 4 or 5, wherein the upper limit voltage and the lower limit voltage of each voltage range can be arbitrarily changed by changing the value set in the register. 7. The voltage distribution measuring means samples and holds the gap average voltage output from the gap average voltage detecting means at predetermined intervals, and outputs the sample and hold circuit. The output of the sample and hold circuit is a digital signal. To an A / D conversion circuit for converting into an A / D conversion circuit, a code conversion circuit for outputting the output from the A / D conversion circuit by dividing the output into several preset voltage ranges, and a corresponding voltage range from the code conversion circuit. 4. The discharge according to claim 1, wherein the output signal is constituted by a frequency counter for each voltage range that counts up in synchronization with the execution of the sample and hold if there is an output signal. Processing status monitoring device for processing machines. 8. The voltage distribution measuring means includes a sample hold circuit for sample-holding and outputting the gap average voltage output by the gap average voltage detecting means at predetermined intervals, and a digital output for the sample-hold circuit. A / D converter for conversion, memory means for storing the output value from the A / D converter at an address which is sequentially updated in synchronization with the execution of the sample hold for a preset time length, and the memory 3. The statistical processing means for counting the number of values included in each voltage range among the values stored in the means for each voltage range, and the statistical processing means. Alternatively, the machining status monitor device of the electric discharge machine according to claim 3.