JPS6244316A - Power supply condition monitor for electric discharge machine - Google Patents

Abstract

PURPOSE:To enable monitoring of the power supply condition by comparing the output from differential amplifier corresponding with the difference of current between upper and lower power suppliers with perdetermined level and deciding the power supply condition on the basis of output condition under occurrence of check pulse in the discharge interval. CONSTITUTION:When the current level of one of detectors 10, 11 is low, the output from differential amplifier 16 corresponding with the difference is compared with referential voltage through one of the comparators 17, 18 thus to produce 1 from OR gate 19. While check pulse is produced from a pulse power source 5 through pulse generator 13 and passed through AND gate 20 and OR gate 21 to se the flipflop 22 thus to light the display element 30. When both currents are low, D.C. voltage added through an adder 27 and converted through integrator 28 is compared through comparator 29 with referential voltage produced by passing the inter-electrode voltage to discharge detector 23 then converting through integrating circuit 24 and if it is low, the output is brought to 1 thus to set the flipflop 22.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is directed to the problem of wire electrode failure that occurs when the current flowing to the upper and lower feeders becomes unbalanced due to poor contact between the wire electrode and the feeder in a wire electrical discharge machine. The present invention relates to a power supply status monitoring device for preventing disconnection.

[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 poor contact occurs between either the upper or lower feeder and the wire electrode due to roughness of the contact surface or adhesion of foreign matter, the current flowing to the upper or lower feeder becomes extremely unbalanced, exceeding the current capacity of the wire electrode. Due to the large current flowing
Wire electrodes tend to break due to abnormal heating.

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 one side feeder) from the state of change of the current, and detecting the presence or absence of concentrated discharge in the same location. When such a problem occurs, there are methods to prevent processing defects and wire breakage by lowering the processing energy, but no consideration has been given to preventing wire breakage caused by the above-mentioned poor contact of the single-side feeder.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a power supply state monitoring device for a wire electric discharge machine that can detect an unbalanced power supply current value due to a contact failure of one side feeder before the wire electrode becomes disconnected.

[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 to detect each,
a differential amplifier that generates an output corresponding to the difference between the feeding current values of the upper and lower feeders detected by the current detector; a circuit that generates a check pulse in a discharge section where a machining current flows through the wire electrode; A comparator that compares the output of the amplifier with a predetermined value, and a circuit that outputs a determination signal as to whether or not the power supply state of the wire electrode is normal based on the output state of the comparator at the time when the check pulse is generated. The present invention is characterized by detecting an abnormal state in which the difference between the feeding current values of the feeding electrons exceeds a predetermined value.

[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, and 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 socket speed switching element driven by the pulse generation signal of the pulse oscillator 4; Processing pulse power is supplied between the wire pole 1 and the workpiece 2 through the lower feeder 7. 8
and 9 are wire running reels. 10 is an upper current detector that detects the feeding current value of the upper feeding element 6; 11 is a lower current detector that detects the feeding current value of the lower feeding element 7;
Each of these current detectors outputs a voltage corresponding to a power supply current value by electromagnetic induction or the like. 12 is a play circuit, 1
3 is a check pulse generation circuit (for example, a one-shot multivibrator), and the check pulse is generated by the clock input (c) of the AND gate 2o and the D-type flip-flop 22.
p is given to the large input.

14 and 15 are amplifiers that amplify the current detection signal; 16
is a differential amplifier, the output signals of the amplifiers 14 and 15 are input manually, and the output of the differential amplifier 16 is input to the comparators 17 and 1.
8 and are compared with reference voltage terminals E1 and -E2, respectively. The outputs of the comparators 17 and 18 are input through an OR gate 19 to an AND gate 20 together with the check pulse. The output of the AND gate 2o is applied to the set input (S input) of a D-type flip-flop 22 through an OR gate 21. The data input (D
Human power) is maintained at the logical value 1101+ level,
The output (Q output) of the flip-flop 22 is sent to the buffer 2.
6 and is supplied to a display element 27 such as an LED.

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 comparator 29.

Further, the output signals of the amplifiers 14 and ]5 are outputted to the adder 2.
7 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 passed through the OR gate 21 to the above-mentioned flip-flop 2.
2 set input (S human power). 25.2
6 is an external resistance of the adder 27.

Next, the operation of this embodiment will be explained.

When electrical discharge machining is performed by supplying pulsed power from the pulse power supply 5 between the wire electrode 1 and the workpiece 2, if the power supply status is normal, all machining current machining is performed using the upper power supply as shown in Fig. 2. It is the sum of the current I0 flowing through the lower feeder 7 and the current I0 flowing through the lower feeder 7. FIG. 3 shows a state in which the lower feeder 7 has a poor contact or poor connection (I2=o), and in this state, the upper feeder 6 is connected to the
The total machining current flow including the current flow 2 to be flowed. 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 6.7 are detected by the current detectors 10 and 11, respectively, and these current detection signals are sent to the amplifier 14. and 15 and applied to the 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 6.7 is applied to one input of the comparators 17 and 18, They are compared with a reference voltage element E and a predetermined value represented by -E2, respectively. In this way, for example, if Ia is 20 as shown in FIG. 3, only the output of the comparator 18 will be at the level of the logical value 1'1", and conversely, if I,=O, Only the output of the comparator 17 has a logic value of 11'' 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 outputs of the comparators 17 and 18 are both at the logical value II OI+ level.

The output of either one of the comparators 17 and 18 is II I
When it reaches the I+ 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 from the check pulse generation circuit 13 is generated.
The flip-flop 22 is set.

The check pulse is generated by a pulse generation signal (waveform A in FIG. 4) from the pulse oscillator 4 in the play circuit 12 so that the check pulse is generated in the discharge section after a predetermined time has passed after the voltage is applied between the electrodes by the pulse power source 5. This is synchronized to a delayed signal.

When the D-type flip-flop 22 is set in this way, the output (Q) signal of the flip-flop is held at the logic value rt 1 u level, so that the display element 27 is energized through the buffer 26 and an abnormal state is detected. Display the status.

The above describes the function of detecting and displaying the status when one side feeder (lower feeder in Figure 3) has a contact failure. Even if this happens, a function has been added to detect and display the situation.

Next, the latter operation will be explained.

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 FIG. 4) is integrated by an integrating circuit 24 and converted into a DC voltage at a predetermined level, which is then output to a comparator 2.
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 feeder 6.7 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 sent to the adder 2.
7 and find the sum of both.

Adder 27 corresponding to the total machining current value obtained by this
The output is integrated by an integrator 28, converted to 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 passed through the OR gate 21 to the set input of the D-type flip-flop 22. is given, putting the flip-flop 22 in the set state. Therefore, the output (Q) signal of the flip-flop 22 has a logic value of It I
It becomes I+ level, and the display element 27 passes through the buffer 26.
energizes and displays an abnormal condition.

The above embodiment aims to reduce the cost of the device by using a simple circuit that simply indicates whether the power supply status is correct or not using a display element such as an LED. Signal for detecting unbalance (first
In order to prevent the wire electrode from breaking, a circuit configuration may be adopted in which the machining pulse energy is controlled to be lowered by using the output signal of the AND gate 20 in the figure).

〔Effect of the invention〕

According to the present invention, 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 electric discharge machining is detected, and abnormality display and machining pulse energy control are performed. This prevents wire breakage due to abnormal heating of the wire electrode.
It is possible to avoid functional deterioration due to wire breakage in the wire electrical discharge machine, which should originally be operated unmanned.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 is a state diagram when the power supply to the wire electrode is normal, and Fig. 3 is a state diagram when the lower feeder has poor contact. 4 are diagrams showing voltage waveforms of important parts in FIG. 1. 1... Wire electrode 2... Processed product 5... Pulse power supply 6... Upper side feeder 7... Lower side feeder
10...Upper current detector 11...Lower current detector 13...Check pulse generation circuit 16...Differential amplifier 17.18...Comparator 20...Signal for determining whether the power supply status is correct or not AND gate that outputs

Claims (1)

[Claims] In a wire electrical discharge machine that performs electrical discharge machining by supplying pulsed power between a wire electrode and a workpiece through feeders installed above and below the workpiece from a pulse power source, the current used to detect the feed current value of each of the upper and lower feeders. A detector, a differential amplifier that generates an output corresponding to the difference between the feeding current values of the upper and lower feeders detected by the current detector, and a circuit that generates a check pulse in a discharge section where a machining current flows through the wire electrode. , a comparator that compares the output of the differential amplifier with a predetermined value;
A power supply state monitoring device for a wire electric discharge machine, comprising: a circuit that outputs a determination signal as to whether or not the power supply state of the wire electrode is normal based on the output state of the comparator at the time when the check pulse is generated.