JPH0521691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is directed to a wire electrical discharge machining machine in which the current flowing through the upper and lower feeders becomes unbalanced due to poor contact between the wire electrode and the feeder. The present invention relates to a power supply state monitoring device for preventing disconnection and detecting that a total power supply current value has decreased from a normal value.

[Background of the invention]

In wire electric discharge machines, machining pulse power is generally supplied between the wire electrode and the workpiece from a pulse power source through feeders placed above and below the workpiece, and if the power supply status is normal, the machining current is The current is divided into two parts: upper and lower feeders. However, if a poor contact occurs between either the upper or lower feeder and the wire electrode due to roughness on the contact surface or adhesion of foreign matter, the current flowing through the upper and lower feeders becomes extremely unbalanced, and the current capacity of the wire electrode increases. Because a large current exceeding

Conventionally, as described in Japanese Patent Application Laid-open No. 59-30620, the presence or absence of concentrated discharge is determined by detecting the current flowing in the upper and lower feeders (or single-side feeder) from the state of change in the current, and detecting concentrated discharge in the same location. When this occurs, there are methods to prevent defective machining and wire breakage by lowering the machining energy, but it is difficult to prevent wire breakage caused by contact failure of the single-side feeder and to abnormally reduce the total feed current value. No consideration was given to the resulting deterioration in the functionality of the wire electrical discharge machine.

[Purpose of the invention]

An object of the present invention is to be able to detect a state in which the power supply current value becomes unbalanced due to a contact failure of one-side feeder before the wire electrode becomes disconnected, and also to make it possible to detect the state in which the power supply current value becomes abnormal compared to the normal reference current value. It is an object of the present invention to provide a power supply status monitoring device for a wire electrical discharge machine that can detect even when the power supply status has decreased.

[Summary of the invention]

The present invention provides a wire electrical discharge machine that performs electric discharge machining by supplying pulsed power between a wire electrode and a workpiece through feeders provided above and below the workpiece from a pulse power source, and the present invention provides a wire electrical discharge machine that performs electric discharge machining by supplying pulsed power from a pulse power supply through feeders provided above and below the workpiece. A current detector detects each, a differential amplifier generates an output corresponding to the difference in the feeding current value of the upper and lower feeders detected by the current detector, and a check pulse is applied to the discharge section where the machining current flows through the wire electrode. The generated circuit and the output of the differential amplifier are compared with a positive predetermined value (+E ₁ ) and a negative predetermined value (−E ₂ ), respectively, and the differential amplifier output is larger than the positive predetermined value. A first comparator that generates an output when the check pulse is generated and a second comparator that generates an output when the check pulse is smaller than a predetermined negative value. A logic circuit that determines that the value is unbalanced and outputs an unbalance determination signal, an adder that adds the upper and lower feed current values detected by the current detector and outputs it as a total machining current value, and a A circuit that calculates and outputs a reference current value corresponding to the total machining current value in a normal state by detecting the arc voltage at which a third comparator that outputs an abnormal decrease determination signal of the total machining current value when the total machining current value is smaller than the reference current value; an abnormal signal output circuit that outputs an abnormal signal from an output terminal Q when any discrimination signal is generated in response to the input terminal S; and a display means that displays an abnormality in the power supply state to the wire electrode by the output of the abnormal signal output circuit. The present invention is characterized by having a configuration including the following.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of the embodiment, where 1 is a wire electrode;
2 is a processed product, 3 is a nozzle for supplying processing liquid, 4 is a pulse oscillator, 5 is a pulse power source including a DC power source and a high-speed switching element driven by the pulse generation signal of the pulse oscillator 4, Processing pulse power is supplied between the wire electrode 1 and the workpiece 2 through the side feeder 7. 8 and 9 are wire running reels. 10 is an upper current detector that detects the current value of the upper feeder 6, and 11 is a lower current detector that detects the current value of the lower feeder 7. These current detectors are each powered by electromagnetic induction or the like. Outputs voltage corresponding to current value. 12
13 is a delay circuit, 13 is a check pulse generation circuit (for example, a one-shot multivibrator),
The check pulse is the clock input ( _CP input) of the AND gate 20 and the D-type flip-flop 22.
given to. 14 and 15 are amplifiers that amplify the current detection signal; 16 is a differential amplifier, into which the output signals of the amplifiers 14 and 15 are input; When the differential amplifier output is greater than the positive reference voltage, and smaller than the negative reference voltage, the differential amplifier output is compared with the reference voltages +E ₁ and -E ₂ by the first and second comparators 17, Each of the 18 outputs has a logic value of "1" level. The comparators 17, 18
The output of is passed through OR gate 19 to AND gate 20
is input together with the check pulse.
The output of the AND gate is applied through an OR gate 21 to a set input (S input) of a D-type flip-flop 22. The data input (D input) of the flip-flop 22 is maintained at the logical "0" level, and the output (Q output) of the flip-flop 22 is maintained at the logic "0" level.
is the display element 3 such as LED through the buffer 30.
1.

On the other hand, a detection signal from a discharge detector 23 that detects discharge from the voltage between electrodes is input to an integrator 24, and an output signal from the integrator 24 is applied to one input of a third comparator 29.

Further, the output signals of the amplifiers 14 and 15 are added by an adder 27, and the output thereof is applied to the other input of the comparator 29 through an integrator 28. The output of the comparator 29 is applied through an OR gate 21 to the set input (S input) of the D-type flip-flop 22. 25 and 26 are external resistances of the adder 27.

Next, the operation of this embodiment will be explained.

A pulse power source 5 is connected between the wire electrode 1 and the workpiece 2.
When performing electrical discharge machining by supplying pulse power from
If the power supply status is normal, as shown in Figure 2,
The total machining current is the sum of current ₁ flowing through the upper feeder 6 and current ₂ flowing through the lower feeder 7. FIG. 3 shows a state in which the lower feeder 7 has a poor contact or poor connection ( ₂ = 0), and in this state, the current ₁ that should flow in the upper feeder 6 and the current that should flow in the lower feeder 7 are as follows. flows. Therefore, since the machining current flows only in the portion of the wire electrode 1 above the discharge point P, the current value exceeds the current capacity of the wire electrode, and wire breakage is likely to occur due to abnormal heating.
Therefore, if machining is to be continued in the state shown in FIG. 3, the current value must be lowered.

In this embodiment, in order to detect such an abnormality in the power supply state and notify the operator, the power supply current values of the upper and lower feeders 6 and 7 are detected by the current detectors 10 and 11, respectively.
The current detection signals are detected by the amplifier 14.
and 15 and fed to a differential amplifier 16, and the output of the differential amplifier 16 corresponding to the difference in the feeding current values of the upper and lower feeders 6 and 7 is applied to the first comparator 17 and the second comparator 18. When the differential amplifier output _is greater than the _positive reference voltage and less than the negative reference voltage, the differential amplifier output is The outputs of the first and second comparators 17 and 18 are set to the logic "1" level, respectively. In this way, for example, when ₂ = 0 as shown in Fig. 3, only the output of the comparator 18 will be at the logic value "1" level, and conversely, when ₁ = 0, the comparator 18 will Only the output of No. 17 has a logical "1" level. In a normal power supply state in which the output of the differential amplifier 16 is within a predetermined value on the (+) side and the (-) side, the comparators 17 and 18 are both at the logic "0" level.

When the output of either one of the comparators 17 and 18 goes to the "1" level, this output signal passes through the AND gate 20 and is input to the D-type flip-flop 22 at the time when the check pulse is generated from the check pulse generating circuit 13. Put the flip-flop 22 into the set state.

The check pulse is generated by transmitting the pulse generation signal (waveform A in FIG. 4) from the pulse oscillator 4 to the delay circuit 12 so that the check pulse is generated in the discharge section after a predetermined time has elapsed since the voltage is applied between the poles by the pulse power supply 5.
It is synchronized to a delayed signal through the .

When the D-type flip-flop 22 is set in this manner, the output Q signal of the flip-flop is held at the logic "1" level, so that the display element 31 is energized through the buffer 30 to display an abnormal state.

The above describes the function of detecting and displaying the condition when one side feeder (lower feeder in Figure 3) has a poor contact. Even if it becomes
A function is added to detect and display the status.

Next, the operation of detecting and displaying that contact failure has occurred in both the upper and lower feeders will be described.

Even if the contact between the upper and lower feeders 6, 7 and the wire electrode 1 is poor, if a discharge occurs between the electrodes and a machining current of several amperes flows, the voltage between the electrodes will increase as shown in waveform B in Figure 4. Since this becomes an arc voltage, this is detected by the discharge detector 23. This discharge detection signal (waveform C in Figure 4) is integrated by the integrating circuit 24,
The third comparator 2 converts it into a DC voltage of a predetermined level.
9 to one input. This input signal is, so to speak, a signal corresponding to an ideal reference current value (predetermined processing current value) when the contact state between the feeders 6 and 7 and the wire electrode 1 is normal. On the other hand, signals corresponding to the upper feeding current value and the lower feeding current value from the amplifiers 14 and 15 are input to the adder 27, and the sum of these two is calculated.

The output of the adder 27 corresponding to the total machining current value thus obtained is integrated by the integrator 28, converted into a DC voltage, and applied to the other input of the comparator 29.

By doing this, when the total machining current value is lower than the reference current value, the output of the comparator 29 becomes a logic "1" level, and this signal is applied to the set input of the D-type flip-flop 22 through the OR gate 21. The flip-flop 22 is placed in the set state. Therefore, the flip-flop 2
The logical value of the output Q signal of 2 becomes "1" level,
Power is applied to the display element 31 through the buffer 30 to display an abnormal state.

The above embodiment is intended to reduce the cost of the device by using a simple circuit that simply displays the success or failure of the power supply status using a display element such as an LED. In order to prevent wire electrode breakage, the circuit configuration may be such that the machining pulse energy is controlled to be lowered by using a signal for detecting the unbalance (the output signal of the AND gate 20 in Fig. 1). can.

〔Effect of the invention〕

According to the present invention, it is possible to detect a state in which the feed current values of the upper and lower feeders become unbalanced due to poor contact between the feeder and the wire electrode during wire electrical discharge machining, and a state in which the total feed current value has decreased from its normal value. Since it is possible to perform abnormality display and control of machining pulse energy, it is possible to prevent wire breakage due to abnormal heating of the wire electrode, and prevent wire breakage and abnormalities in the total power supply current value of the wire electrical discharge machine, which should normally be operated unmanned. Functional deterioration due to deterioration can be avoided.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure shows the state when the power supply to the wire electrode is normal, Figure 3 shows the state when the lower feeder has poor contact, and Figure 4 shows the voltage waveform of the main part in Figure 1. FIG. 1... Wire electrode, 2... Processed product, 5... Pulse power supply, 6... Upper feeder, 7... Lower feeder,
10... Upper current detector, 11... Lower current detector, 13... Check pulse generation circuit, 16...
Differential amplifier, 17, 18...first comparator, second
comparator, 20...AND gate that outputs a signal for determining whether the power supply status is correct or not.

Claims (1)

[Scope of Claims] 1. A wire electrical discharge machine that performs electrical discharge machining by supplying pulse power between a wire electrode and a workpiece through feeders provided above and below the workpiece from a pulse power source, (a) Current detectors 10 and 11 that detect the feeding current values of the electrons 6 and 7, respectively; (b) a differential amplifier 16 that produces an output corresponding to the difference between the detected feeding current values; and (c) a wire electrode 1. (d) Compare the output of the differential amplifier 16 with a positive predetermined value (+E ₁ ) and a negative predetermined value (−E ₂ ), respectively. a first comparator 17 that generates an output when the differential amplifier output is larger than a predetermined positive value; and a second comparator 18 that generates an output when the output of the differential amplifier is smaller than a predetermined negative value. Logic circuits 19 and 20 that determine that the upper and lower power supply current values are unbalanced based on output generation from either of the first and second comparators 17 and 18 at the time when the check pulse is generated, and output an unbalance determination signal. (f) an adder 27 that adds the upper and lower feed current values detected by the current detectors 10 and 11 and outputs the result as a total machining current value; and (g) detects an arc voltage generated during electric discharge machining. circuits 23 and 24 that calculate and output a reference current value corresponding to the total machining current value under normal conditions;
(H) Compare the magnitude of this reference current value and the total machining current value from the adder 27, and when the total machining current value is smaller than the reference current value, output an abnormal decrease determination signal of the total machining current value. a third comparator 29; (i) the abnormal decrease determination signal from the third comparator 29 and the unbalance determination signal from the logic circuits 19 and 20 to the input terminal S via the OR circuit 21; an abnormality signal output circuit 22 which outputs an abnormality signal from an output terminal Q when any of the discrimination signals is generated; A power supply state monitoring device for a wire electrical discharge machine, comprising: means 31;